I have just replaced the seal and bearings on my  Yanmar YSE12 water pump. 
It now pumps water and does not leak, but it doesn't seem to produce enough 
pressure to push water through the exhaust. The impellor is not new but 
looks fine. My question is, what else can I do to recondition the pump? I 
have tried grinding and polishing the face plate - it is fairly smooth 
although there is a very slight bump in the middle where the impellor has 
not worn it. The interior of the pump isn't perfectly smooth but neither is 
it seriously scored. I also had the shaft skimmed where the seal goes, to 
remove some scoring. Any ideas of what else I should try and if all else 
fails, are replacements available?
TIA John.

"John Seager"  wrote in message 
news:vbidnX3mktnWACDVnZ2dnUVZ8tfinZ2d@saix.net...
>I have just replaced the seal and bearings on my  Yanmar YSE12 water pump. 
>It now pumps water and does not leak, but it doesn't seem to produce enough 
>pressure to push water through the exhaust. The impellor is not new but 
>looks fine. My question is, what else can I do to recondition the pump? I 
>have tried grinding and polishing the face plate - it is fairly smooth 
>although there is a very slight bump in the middle where the impellor has 
>not worn it. The interior of the pump isn't perfectly smooth but neither is 
>it seriously scored. I also had the shaft skimmed where the seal goes, to 
>remove some scoring. Any ideas of what else I should try and if all else 
>fails, are replacements available?
> TIA John.

The impeller may look fine, but check that the brass bush can't turn inside 
the blades.

Alisdair

John Seager wrote:

> I have just replaced the seal and bearings on my  Yanmar YSE12 water pump.
> It now pumps water and does not leak, but it doesn't seem to produce
> enough pressure to push water through the exhaust. The impellor is not new
> but looks fine. My question is, what else can I do to recondition the
> pump?

Have you considered the possibility that there is (now) nothing wrong with
the pump?  If the pump has been dodgy in the past, it may have let the
exhaust get too hot.  This could have caused the exhaust hose to delaminate
internally, leading to narrowing of the bore in places, making it more
difficult for water to get through.

"Alisdair Gurney"  wrote in message 
news:g9kbl1$r42$1$8302bc10@news.demon.co.uk...
>
> The impeller may look fine, but check that the brass bush can't turn 
> inside the blades.
That did happen the first time around but I spotted it. The replacement 
impellor seems to pump OK, although I suppose it could still be slipping a 
bit. I'll check again.
Thanks. J

"Ronald Raygun" <no.spam@localhost.localdomain> wrote in message 
news:eHjvk.52143$E41.24637@text.news.virginmedia.com...
> Have you considered the possibility that there is (now) nothing wrong with
> the pump?  If the pump has been dodgy in the past, it may have let the
> exhaust get too hot.  This could have caused the exhaust hose to 
> delaminate
> internally, leading to narrowing of the bore in places, making it more
> difficult for water to get through.
>
I don't think this happened because it failed on first start up and I always 
check for water coming out of the exhaust. When it failed, I switched off 
well before things got hot. However, I will check that the water injection 
point isn't somehow blocked. Not so sure how to check the exhaust hose but 
I'll take a look.

BTW does anyone know what sort of flow the pump should produce? It pumps 
quite a steady stream but only with a head of about 30cm. I would have 
thought it might  produce  a fairly strong jet with no back pressure.
John.

On Wed, 3 Sep 2008 12:26:15 +0200, "John Seager" 
wrote:

>
>"Ronald Raygun" <no.spam@localhost.localdomain> wrote in message 
>news:eHjvk.52143$E41.24637@text.news.virginmedia.com...
>> Have you considered the possibility that there is (now) nothing wrong with
>> the pump?  If the pump has been dodgy in the past, it may have let the
>> exhaust get too hot.  This could have caused the exhaust hose to 
>> delaminate
>> internally, leading to narrowing of the bore in places, making it more
>> difficult for water to get through.
>>
>I don't think this happened because it failed on first start up and I always 
>check for water coming out of the exhaust. When it failed, I switched off 
>well before things got hot. However, I will check that the water injection 
>point isn't somehow blocked. Not so sure how to check the exhaust hose but 
>I'll take a look.
>
>BTW does anyone know what sort of flow the pump should produce? It pumps 
>quite a steady stream but only with a head of about 30cm.
> I would have 
>thought it might  produce  a fairly strong jet with no back pressure.

Are the channels the water uses to flow through the engine water jacket clogged
up?

If you remove the thermostat, does the engine run cold?
-- 

Martin

John Seager wrote:

> It pumps quite a steady stream but only with a head of about 30cm.

Do you mean the input head needs to be 30cm for it to work at all?
Or that the output head it produces is only 30cm?  Neither sounds
healthy.

Run it with the water coming in from a bucket, i.e. disconnect the
input hose from the skin fitting and dip the end into a bucket full
of water.  You may need to prime the hose and elevate the bucket to
supply the necessary head.  With the engine running, and water being
sucked out of the bucket, stick your hand in the bucket and put your
thumb over the end of the hose.  You ought to feel a good strong suck.

If not, something's wrong.  There could be an air leak on the input
side.  With the engine off, lift the inlet hose up high and fill it up
to the brim with water.  Does it trickle away?  If so, where does it go?
If you can spot the leak on the hose itself or at the connection to the
pump, you've found it.  Otherwise, or if it doesn't leak away:

Disconnect the pump's outlet hose.  Fill the input hose, held high
as before, with water.  Does the water flow through the pump and
emerge at the output side?  You may need to blow on the input side
to persuade it through.  If this happens, the impeller isn't
sealing properly to the back wall or faceplace.  Could be because
the face plate isn't on tight enough (gasket too thick) or the
impeller is too small.

"Ronald Raygun" <no.spam@localhost.localdomain> wrote in message 
news:r9vvk.52373$E41.27588@text.news.virginmedia.com...
> John Seager wrote:
>
>> It pumps quite a steady stream but only with a head of about 30cm.
>
> Do you mean the input head needs to be 30cm for it to work at all?
> Or that the output head it produces is only 30cm?  Neither sounds
> healthy.
>
> Run it with the water coming in from a bucket, i.e. disconnect the
> input hose from the skin fitting and dip the end into a bucket full
> of water.  You may need to prime the hose and elevate the bucket to
> supply the necessary head.  With the engine running, and water being
> sucked out of the bucket, stick your hand in the bucket and put your
> thumb over the end of the hose.  You ought to feel a good strong suck.
>
> If not, something's wrong.  There could be an air leak on the input
> side.  With the engine off, lift the inlet hose up high and fill it up
> to the brim with water.  Does it trickle away?  If so, where does it go?
> If you can spot the leak on the hose itself or at the connection to the
> pump, you've found it.  Otherwise, or if it doesn't leak away:
>
> Disconnect the pump's outlet hose.  Fill the input hose, held high
> as before, with water.  Does the water flow through the pump and
> emerge at the output side?  You may need to blow on the input side
> to persuade it through.  If this happens, the impeller isn't
> sealing properly to the back wall or faceplace.  Could be because
> the face plate isn't on tight enough (gasket too thick) or the
> impeller is too small.

Lots of food for thought here - thanks!
1. I meant that it only produces a head of about 30cm. I didn't expect the 
outflow to hit the roof but its closer to a  'trickle' than a 'gush'.
2. An air leak on the suction side seems possible - even a small one might 
greatly reduce the flow. The gasket is home made and reasonably thin (glossy 
paper and a bit of silicone) but the wear on both impellor and bore could 
reduce efficiency (the pump is nearly 30 years old).
3. I'll try your suggested checks to see how well it sucks and where the 
water goes if left alone.
Thanks again. John.

"Martin" <me@address.invalid> wrote in message 
news:erpsb41nbuqcpcpoko57nbj8iu8sbb94gl@4ax.com...
> On Wed, 3 Sep 2008 12:26:15 +0200, "John Seager" 
> 
> wrote:
>
> Are the channels the water uses to flow through the engine water jacket 
> clogged
> up?
>
> If you remove the thermostat, does the engine run cold?
> -- 
>
> Martin
>
Engine jacket is clear - I can blow through it easily enough. Showing my 
ignorance but I'm not sure about a thermostat, don't think it has one, it's 
raw water cooled. J

On Wed, 3 Sep 2008 17:15:02 +0200, "John Seager" 
wrote:

>
>"Martin" <me@address.invalid> wrote in message 
>news:erpsb41nbuqcpcpoko57nbj8iu8sbb94gl@4ax.com...
>> On Wed, 3 Sep 2008 12:26:15 +0200, "John Seager" 
>> 
>> wrote:
>>
>> Are the channels the water uses to flow through the engine water jacket 
>> clogged
>> up?
>>
>> If you remove the thermostat, does the engine run cold?
>> -- 
>>
>> Martin
>>
>Engine jacket is clear - I can blow through it easily enough. Showing my 
>ignorance but I'm not sure about a thermostat, don't think it has one,

I couldn't find one in the manual

Impeller part number is r04211- 4207 0

"Pump should deliver
YSE 12
460 lit.,/hr. (Pump shalt speed 1900 rpm, Crankshaft speed 3000 rpm)
If operated *without water, the rubbber impeller will burn)"

> it's 
>raw water cooled. J 
>

Do you know you can download an English language version manual and a parts list
from  http://www.motoren.ath.cx/

6.12 Water Cooling Failure in YSE 8 12 Manual made me smile.
-- 

Martin

On Wed, 3 Sep 2008 17:15:02 +0200, "John Seager" 
wrote:

>
>"Martin" <me@address.invalid> wrote in message 
>news:erpsb41nbuqcpcpoko57nbj8iu8sbb94gl@4ax.com...
>> On Wed, 3 Sep 2008 12:26:15 +0200, "John Seager" 
>> 
>> wrote:
>>
>> Are the channels the water uses to flow through the engine water jacket 
>> clogged
>> up?
>>
>> If you remove the thermostat, does the engine run cold?
>> -- 
>>
>> Martin
>>
>Engine jacket is clear - I can blow through it easily enough. Showing my 
>ignorance but I'm not sure about a thermostat, don't think it has one, it's 
>raw water cooled. J 
>

I found this is in Yanmar Diesel Instruction Manual
(5) Thermostat for cooling water is equipped as standard for better
performance in cold weather.
-- 

Martin

"Martin" <me@address.invalid> wrote in message 
news:5matb459ng4r8hetvsr7n75ke2kt3uf0i8@4ax.com...
> On Wed, 3 Sep 2008 17:15:02 +0200, "John Seager" 
> 
> wrote:
>
> Impeller part number is r04211- 4207 0
>
> "Pump should deliver
> YSE 12
> 460 lit.,/hr. (Pump shalt speed 1900 rpm, Crankshaft speed 3000 rpm)
> If operated *without water, the rubbber impeller will burn)"
>
> Do you know you can download an English language version manual and a 
> parts list
> from  http://www.motoren.ath.cx/
>
> 6.12 Water Cooling Failure in YSE 8 12 Manual made me smile.
> -- 
>
> Martin

Many thanks for this. The flow rate info should help me estimate whether its 
pumping anything like the amount of water it should. I think a new impeller 
sounds like a good idea too, just to be sure that it's 100% OK.
J.

On 2 Sep, 21:07, "John Seager"  wrote:
> I have just replaced the seal and bearings on my  Yanmar YSE12 water pump.
> It now pumps water and does not leak, but it doesn't seem to produce enough
> pressure to push water through the exhaust. The impellor is not new but
> looks fine. My question is, what else can I do to recondition the pump? I
> have tried grinding and polishing the face plate - it is fairly smooth
> although there is a very slight bump in the middle where the impellor has
> not worn it. The interior of the pump isn't perfectly smooth but neither is
> it seriously scored. I also had the shaft skimmed where the seal goes, to
> remove some scoring. Any ideas of what else I should try and if all else
> fails, are replacements available?
> TIA John.

I have a YSM8 and I have had to rebuild the water pump two years ago.
I put in a new shaft, bearings and seals. I was advised to replace the
body but I felt they wanted too much for it. It still leaked for
another year but in this last year the seals seemed to have started to
do what they are supposed to do and it has stopped leaking. I have
never had a problem with exhaust water not coming out even when the
pump was leaking like a sieve. I do have a relatively new u-bend at
the start of the exhaust system, which I understand rusts out with raw
water cooling and can block the system. Also check the tension of your
water pump belt, although mine seems to run quite happily with over an
inch of play in it.

"LeeShore"  wrote in message 
news:ccd17fd3-c0dd-44fd-81dc-d2fa08f12fc0@y38g2000hsy.googlegroups.com...
>I have a YSM8 and I have had to rebuild the water pump two years ago.
>I put in a new shaft, bearings and seals. I was advised to replace the
>body but I felt they wanted too much for it. It still leaked for
>another year but in this last year the seals seemed to have started to
>do what they are supposed to do and it has stopped leaking. I have
>never had a problem with exhaust water not coming out even when the
>pump was leaking like a sieve. I do have a relatively new u-bend at
>the start of the exhaust system, which I understand rusts out with raw
>water cooling and can block the system. Also check the tension of your
>water pump belt, although mine seems to run quite happily with over an
>inch of play in it.

After various helpful posts I think I must check the pump thoroughly for 
leaks first. It doesn't leak water (now), but an air leak on the suction 
side could be just as bad, if not worse. I'll try running the outlet in a 
bucket to see if it's blowing bubbles.

I will also check the exhaust water injection point for free flow - it is in 
an old and rusty swan neck and I suppose it could be blocked.
John.

John Seager wrote:
> I have just replaced the seal and bearings on my  Yanmar YSE12 water pump. 
> It now pumps water and does not leak, but it doesn't seem to produce enough 
> pressure to push water through the exhaust. The impellor is not new but 
> looks fine. My question is, what else can I do to recondition the pump? I 
> have tried grinding and polishing the face plate - it is fairly smooth 
> although there is a very slight bump in the middle where the impellor has 
> not worn it. The interior of the pump isn't perfectly smooth but neither is 
> it seriously scored. I also had the shaft skimmed where the seal goes, to 
> remove some scoring. Any ideas of what else I should try and if all else 
> fails, are replacements available?
> TIA John. 

Errr excuse me,
The waterpump doesn't pushes the water out of the exhaust. That is what 
the exhaust fumes do. The pump injects the water in the elbow of the 
exhaust en it gets collected in the waterlock. Then the exhaust fumes 
pushes the water out in blobs.
Depending if you have intercooling or raw water cooling you might need 
to descale the intercooler or the motor in order to get a larger flow. 
It be blocked by deposits and than the resistance is too high for a 
decent flow.

regards,
Norbert

"Norbert Koster"  wrote in message 
news:48c2d08f$0$196$e4fe514c@news.xs4all.nl...

> Errr excuse me,
> The waterpump doesn't pushes the water out of the exhaust. That is what 
> the exhaust fumes do. > It be blocked by deposits and than the resistance 
> is too high for a decent flow.
>
Thanks. You're quite correct. I guess I meant that it doesn't have enough 
power to push water as far as the injetion elbow, even though it pumps when 
the hose is disconnected. It's raw water cooled, so there isn't much to get 
blocked, and I can blow through tthe engine OK. I'll check for blockages at 
the elbow.
John.

On Mon, 8 Sep 2008 12:58:22 +0200, "John Seager" 
wrote:

>
>"Norbert Koster"  wrote in message 
>news:48c2d08f$0$196$e4fe514c@news.xs4all.nl...
>
>> Errr excuse me,
>> The waterpump doesn't pushes the water out of the exhaust. That is what 
>> the exhaust fumes do. > It be blocked by deposits and than the resistance 
>> is too high for a decent flow.
>>
>Thanks. You're quite correct. I guess I meant that it doesn't have enough 
>power to push water as far as the injection elbow, even though it pumps when 
>the hose is disconnected. It's raw water cooled, so there isn't much to get 
>blocked, and I can blow through tthe engine OK. I'll check for blockages at 
>the elbow.

Did you download the manual and read it's suggestions, John?
-- 

Martin

Norbert Koster wrote:

> John Seager wrote:
>> I have just replaced the seal and bearings on my  Yanmar YSE12 water
>> pump. It now pumps water and does not leak, but it doesn't seem to
>> produce enough pressure to push water through the exhaust.
> 
> Errr excuse me,
> The waterpump doesn't pushes the water out of the exhaust. That is what
> the exhaust fumes do. The pump injects the water in the elbow of the
> exhaust en it gets collected in the waterlock. Then the exhaust fumes
> pushes the water out in blobs.

Your criticism is unjustified.  Whilst it is indeed the exhaust gases
which actually push the water out, the water pump must produce a greater
pressure than is present in the exhaust, because otherwise water and/or
exhaust gas would get pushed back into (and through) the pump.  So John
was quite right to say "produce enough pressure to push it through".

John Seager wrote:

> Thanks. You're quite correct. I guess I meant that it doesn't have enough
> power to push water as far as the injetion elbow, even though it pumps
> when the hose is disconnected. It's raw water cooled, so there isn't much
> to get blocked, and I can blow through tthe engine OK. I'll check for
> blockages at the elbow.

Here's another idea:

I'm thinking back to when you said the pump only produces a 30cm head on
the output.  How did you measure this?  By attaching a hose to its outlet
with nothing on the other end, and noting that trickle stopped when you
held the end up 30cm higher than the pump?

If so, then what was connected to the pump's inlet at the time?  The
usual skin fitting?  If so, could it simply be that the pump is actually
situated 30cm below the waterline (you can check this by disconnecting
the inlet hose from the pump, leaving it attached to the skin fitting,
and seeing how far up you need to hold it before water stops pouring
into the boat), and that the pump is therefore adding no pressure
at all?  If so, did you happen to note whether the pump still "produces"
this head even when it isn't spinning, i.e. when the engine is stopped?

If so, it would confirm my earlier suspicion that the pump may have
an internal inlet-outlet leak, i.e. it just passes everything through.
If not, are you sure the fillet is still present?  That's the bit in
the pump chamber which deforms the impeller vanes as they go past.

If the impeller is old and tired, the vanes may not be un-deforming
quickly enough once they've gone past the fillet.  If a new impeller
doesn't fix the problem, you could try temporarily replacing the
pump cover with a bit of perspex sheet so you can see what's going
on inside.  Or just run it briefly with the cover off (and the seacock
closed).

Ronald Raygun wrote:
> Norbert Koster wrote:
> 
>> John Seager wrote:
>>> I have just replaced the seal and bearings on my  Yanmar YSE12 water
>>> pump. It now pumps water and does not leak, but it doesn't seem to
>>> produce enough pressure to push water through the exhaust.
>> Errr excuse me,
>> The waterpump doesn't pushes the water out of the exhaust. That is what
>> the exhaust fumes do. The pump injects the water in the elbow of the
>> exhaust en it gets collected in the waterlock. Then the exhaust fumes
>> pushes the water out in blobs.
> 
> Your criticism is unjustified.  Whilst it is indeed the exhaust gases
> which actually push the water out, the water pump must produce a greater
> pressure than is present in the exhaust, because otherwise water and/or
> exhaust gas would get pushed back into (and through) the pump.  So John
> was quite right to say "produce enough pressure to push it through".
> 
I tend to disagree. The pump must be able to withstand the pressure of 
the fumes, but this is a non constant pressure (pulsating). Only when 
the waterlock is fully loaded the pressure becomes high. At that moment 
the pump must prohibited the backflow of water, which is easy for a 
impeller pump because it is self sealing pump. The pump will still 
deliver some fluid in the engine block for cooling.
Of course when the pump is only producing 30 cm of head, there is 
something seriously wrong. These kinds of pumps must be able to lift 
water at least a couple of meters on a open line. These are displacemnt 
pumps and are not very sensitive for back pressure.
Either there is a blockage in the inlet, like mentioned before, or the 
pump has internal leaks and cannot build enough pressure to lift the 
water. The displacement of fluids (volume swept) of these kind of pumps 
is not very high


regards,
Norbert

John Seager wrote:
> "Norbert Koster"  wrote in message 
> news:48c2d08f$0$196$e4fe514c@news.xs4all.nl...
> 
>> Errr excuse me,
>> The waterpump doesn't pushes the water out of the exhaust. That is what 
>> the exhaust fumes do. > It be blocked by deposits and than the resistance 
>> is too high for a decent flow.
>>
> Thanks. You're quite correct. I guess I meant that it doesn't have enough 
> power to push water as far as the injetion elbow, even though it pumps when 
> the hose is disconnected. It's raw water cooled, so there isn't much to get 
> blocked, and I can blow through tthe engine OK. I'll check for blockages at 
> the elbow.

Try to check the sealing of the pump also. You mustn't be able to blow 
air through the pump. If that does occur you have too much play in the 
pump housing and you either need to replace the shaft sealing (drips 
water) or the cover plate of the pump (too much worn).

regards,
Norbert

"Norbert Koster"  wrote in message 
news:48c58c5e$0$185$e4fe514c@news.xs4all.nl...
> John Seager wrote:
>> "Norbert Koster"  wrote in message 
>> news:48c2d08f$0$196$e4fe514c@news.xs4all.nl...
>>
>>> Errr excuse me,
>>> The waterpump doesn't pushes the water out of the exhaust. That is what 
>>> the exhaust fumes do. > It be blocked by deposits and than the 
>>> resistance is too high for a decent flow.
>>>
>> Thanks. You're quite correct. I guess I meant that it doesn't have enough 
>> power to push water as far as the injetion elbow, even though it pumps 
>> when the hose is disconnected. It's raw water cooled, so there isn't much 
>> to get blocked, and I can blow through tthe engine OK. I'll check for 
>> blockages at the elbow.
>
> Try to check the sealing of the pump also. You mustn't be able to blow air 
> through the pump. If that does occur you have too much play in the pump 
> housing and you either need to replace the shaft sealing (drips water) or 
> the cover plate of the pump (too much worn).
>
> regards,
> Norbert

I remember once in an emergency using Gasket Seal liquid sealant on my water 
pump cover plate. The "temporary" seal lasted 4 seasons!

Dennis.

Dennis Pogson wrote:

> "Norbert Koster"  wrote in message
> news:48c58c5e$0$185$e4fe514c@news.xs4all.nl...
>>
>> Try to check the sealing of the pump also. You mustn't be able to blow
>> air through the pump. If that does occur you have too much play in the
>> pump housing and you either need to replace the shaft sealing (drips
>> water) or the cover plate of the pump (too much worn).
> 
> I remember once in an emergency using Gasket Seal liquid sealant on my
> water pump cover plate. The "temporary" seal lasted 4 seasons!

That just ensures there is no leak between the cover plate and the
pump body.

What I think Norbert has in mind (as have I) with "blowing air through
the pump" is that you can blow into the inlet and it comes out of the
outlet, or vice versa.

On Tue, 09 Sep 2008 09:26:38 GMT, Ronald Raygun <no.spam@localhost.localdomain>
wrote:

>Dennis Pogson wrote:
>
>> "Norbert Koster"  wrote in message
>> news:48c58c5e$0$185$e4fe514c@news.xs4all.nl...
>>>
>>> Try to check the sealing of the pump also. You mustn't be able to blow
>>> air through the pump. If that does occur you have too much play in the
>>> pump housing and you either need to replace the shaft sealing (drips
>>> water) or the cover plate of the pump (too much worn).
>> 
>> I remember once in an emergency using Gasket Seal liquid sealant on my
>> water pump cover plate. The "temporary" seal lasted 4 seasons!
>
>That just ensures there is no leak between the cover plate and the
>pump body.
>
>What I think Norbert has in mind (as have I) with "blowing air through
>the pump" is that you can blow into the inlet and it comes out of the
>outlet, or vice versa.

One could also stick the inlet hose into a 4 litre can of water and measure how
long it takes to pump it empty or even RTFM.

The manual is interesting, there are greasy finger prints on all the pages where
the original owner has had problems.
-- 

Martin

Ronald Raygun wrote:
> Dennis Pogson wrote:
> 
>> "Norbert Koster"  wrote in message
>> news:48c58c5e$0$185$e4fe514c@news.xs4all.nl...
>>> Try to check the sealing of the pump also. You mustn't be able to blow
>>> air through the pump. If that does occur you have too much play in the
>>> pump housing and you either need to replace the shaft sealing (drips
>>> water) or the cover plate of the pump (too much worn).
>> I remember once in an emergency using Gasket Seal liquid sealant on my
>> water pump cover plate. The "temporary" seal lasted 4 seasons!
> 
> That just ensures there is no leak between the cover plate and the
> pump body.
> 
> What I think Norbert has in mind (as have I) with "blowing air through
> the pump" is that you can blow into the inlet and it comes out of the
> outlet, or vice versa.

Correct, if the gasket is blown water will come out every which way and 
that is easy to detect. By coincidence I worked on a hydralic pump today 
which had internal leakage, on the outside no leaks but hardly any 
hydralic pressure, turns out that the pistons were shot.

regards,
Norbert

"John Seager"  wrote in message 
news:vbidnX3mktnWACDVnZ2dnUVZ8tfinZ2d@saix.net...
>I have just replaced the seal and bearings on my  Yanmar YSE12 water pump. 
>It now pumps water and does not leak, but it doesn't seem to produce enough 
>pressure to push water through the exhaust. The impellor is not new but 
>looks fine. My question is, what else can I do to recondition the pump? I 
>have tried grinding and polishing the face plate - it is fairly smooth 
>although there is a very slight bump in the middle where the impellor has 
>not worn it. The interior of the pump isn't perfectly smooth but neither is 
>it seriously scored. I also had the shaft skimmed where the seal goes, to 
>remove some scoring. Any ideas of what else I should try and if all else 
>fails, are replacements available?
> TIA John.
Martin's advice to RTFM is well taken, and I have done so, plus this thread 
has given me loads of other ideas - thanks all. Unfortunately I haven't had 
time to go and check all the ideas yet. In the meantime, I've just been 
quoted GBP 353 (excluding carriage and VAT) for a complete new pump. It 
seemed like a potentially easy way out, but not at that price! I think 
internal leaks seems the most likely cause. I'm going to try the various 
blow through and pumping tests and then strip it again, fit a new impeller 
and see what happens.
John.

"Ronald Raygun" <no.spam@localhost.localdomain> wrote in message 
news:Bc8xk.54778$E41.20512@text.news.virginmedia.com...
> John Seager wrote:
>
>> Thanks. You're quite correct. I guess I meant that it doesn't have enough
>> power to push water as far as the injetion elbow, even though it pumps
>> when the hose is disconnected. It's raw water cooled, so there isn't much
>> to get blocked, and I can blow through tthe engine OK. I'll check for
>> blockages at the elbow.
>
> Here's another idea:
>
> I'm thinking back to when you said the pump only produces a 30cm head on
> the output.  How did you measure this?  By attaching a hose to its outlet
> with nothing on the other end, and noting that trickle stopped when you
> held the end up 30cm higher than the pump?
>
> If so, then what was connected to the pump's inlet at the time?  The
> usual skin fitting?  If so, could it simply be that the pump is actually
> situated 30cm below the waterline (you can check this by disconnecting
> the inlet hose from the pump, leaving it attached to the skin fitting,
> and seeing how far up you need to hold it before water stops pouring
> into the boat), and that the pump is therefore adding no pressure
> at all?  If so, did you happen to note whether the pump still "produces"
> this head even when it isn't spinning, i.e. when the engine is stopped?


Am I that stupid? Quite possibly, but I'm reasonably sure it was pumping
 not just finding its own level. I had it all set up with the engine off and
the outlet hose in my hand. No water was pouring in at that stage - I would
 have noticed (and the crew tends to panic a bit when I allow free flow
of ocean into the boat)!
>
> If so, it would confirm my earlier suspicion that the pump may have
> an internal inlet-outlet leak, i.e. it just passes everything through.
> If not, are you sure the fillet is still present?  That's the bit in
> the pump chamber which deforms the impeller vanes as they go past.
>
> If the impeller is old and tired, the vanes may not be un-deforming
> quickly enough once they've gone past the fillet.  If a new impeller
> doesn't fix the problem, you could try temporarily replacing the
> pump cover with a bit of perspex sheet so you can see what's going
> on inside.  Or just run it briefly with the cover off (and the seacock
> closed).

The fillet/cam looks fine and the impeller blades are very flexible -
possibly more than I would have expected. The manual (yes, I did read it)
 warns you to get the impeller in the right way round, but mine doesn't
 seem to mind being put in wrong. The blades seem able to move back
 and forth depending on the direction of the rotation. I think a new 
impeller
sound like a good idea.

On Wed, 10 Sep 2008 13:37:23 +0200, "John Seager" 
wrote:

>
>"John Seager"  wrote in message 
>news:vbidnX3mktnWACDVnZ2dnUVZ8tfinZ2d@saix.net...
>>I have just replaced the seal and bearings on my  Yanmar YSE12 water pump. 
>>It now pumps water and does not leak, but it doesn't seem to produce enough 
>>pressure to push water through the exhaust. The impellor is not new but 
>>looks fine. My question is, what else can I do to recondition the pump? I 
>>have tried grinding and polishing the face plate - it is fairly smooth 
>>although there is a very slight bump in the middle where the impellor has 
>>not worn it. The interior of the pump isn't perfectly smooth but neither is 
>>it seriously scored. I also had the shaft skimmed where the seal goes, to 
>>remove some scoring. Any ideas of what else I should try and if all else 
>>fails, are replacements available?
>> TIA John.
>Martin's advice to RTFM is well taken,

I hope you appreciated the oily finger prints :o)

> and I have done so, plus this thread 
>has given me loads of other ideas - thanks all. Unfortunately I haven't had 
>time to go and check all the ideas yet. In the meantime, I've just been 
>quoted GBP 353 (excluding carriage and VAT) for a complete new pump. It 
>seemed like a potentially easy way out, but not at that price! I think 
>internal leaks seems the most likely cause. I'm going to try the various 
>blow through and pumping tests and then strip it again, fit a new impeller 
>and see what happens.

Changing the impeller first seems a cheaper way to go.

Before you change it, put your finger over the end of the inlet tube you should
feel it sucking hard. 
-- 

Martin

On Wed, 10 Sep 2008 13:48:10 +0200, "John Seager" 
wrote:

>
>"Ronald Raygun" <no.spam@localhost.localdomain> wrote in message 
>news:Bc8xk.54778$E41.20512@text.news.virginmedia.com...
>> John Seager wrote:
>>
>>> Thanks. You're quite correct. I guess I meant that it doesn't have enough
>>> power to push water as far as the injetion elbow, even though it pumps
>>> when the hose is disconnected. It's raw water cooled, so there isn't much
>>> to get blocked, and I can blow through tthe engine OK. I'll check for
>>> blockages at the elbow.
>>
>> Here's another idea:
>>
>> I'm thinking back to when you said the pump only produces a 30cm head on
>> the output.  How did you measure this?  By attaching a hose to its outlet
>> with nothing on the other end, and noting that trickle stopped when you
>> held the end up 30cm higher than the pump?
>>
>> If so, then what was connected to the pump's inlet at the time?  The
>> usual skin fitting?  If so, could it simply be that the pump is actually
>> situated 30cm below the waterline (you can check this by disconnecting
>> the inlet hose from the pump, leaving it attached to the skin fitting,
>> and seeing how far up you need to hold it before water stops pouring
>> into the boat), and that the pump is therefore adding no pressure
>> at all?  If so, did you happen to note whether the pump still "produces"
>> this head even when it isn't spinning, i.e. when the engine is stopped?
>
>
>Am I that stupid? Quite possibly, but I'm reasonably sure it was pumping
> not just finding its own level. I had it all set up with the engine off and
>the outlet hose in my hand. No water was pouring in at that stage - I would
> have noticed (and the crew tends to panic a bit when I allow free flow
>of ocean into the boat)!
>>
>> If so, it would confirm my earlier suspicion that the pump may have
>> an internal inlet-outlet leak, i.e. it just passes everything through.
>> If not, are you sure the fillet is still present?  That's the bit in
>> the pump chamber which deforms the impeller vanes as they go past.
>>
>> If the impeller is old and tired, the vanes may not be un-deforming
>> quickly enough once they've gone past the fillet.  If a new impeller
>> doesn't fix the problem, you could try temporarily replacing the
>> pump cover with a bit of perspex sheet so you can see what's going
>> on inside.  Or just run it briefly with the cover off (and the seacock
>> closed).
>
>The fillet/cam looks fine and the impeller blades are very flexible -
>possibly more than I would have expected. The manual (yes, I did read it)
> warns you to get the impeller in the right way round, but mine doesn't
> seem to mind being put in wrong. The blades seem able to move back
> and forth depending on the direction of the rotation. I think a new 
>impeller
>sound like a good idea.

I guess you checked the oil level to make sure the water isn't finding it's way
into the sump?
-- 

Martin

"Norbert Koster"  wrote in message 
news:48c58c5e$0$185$e4fe514c@news.xs4all.nl...
> John Seager wrote:

> Try to check the sealing of the pump also. You mustn't be able to blow air 
> through the pump. If that does occur you have too much play in the pump 
> housing and you either need to replace the shaft sealing (drips water) or 
> the cover plate of the pump (too much worn).
>
Regarding the cover plate: is it supposed to be completely flat or should 
there be a slightly raised disc in the middle? I had assumed that the raised 
disc was because the rest of the plate was worn, and therefore ground it 
flat, but I suppose it might have been there from new. In section, mine 
looked like this (greatly exaggerated):
_______=======________
_______________________

and is now, more or less, flat.
_______________________
_______________________

John Seager wrote:

> Regarding the cover plate: is it supposed to be completely flat or should
> there be a slightly raised disc in the middle? I had assumed that the
> raised disc was because the rest of the plate was worn, and therefore
> ground it flat, but I suppose it might have been there from new. In
> section, mine looked like this (greatly exaggerated):
> _______=======________
> _______________________
> 
> and is now, more or less, flat.
> _______________________
> _______________________

If this was caused by wear, would you not have expected the plate
to look as follows?

===_____=======_____===
_______________________

That is to say that the unworn parts would be both in the middle
where there would be less rubbing from the impeller, and also
around the rim where the plate mates with pump's flange?

Also, in the case of wear you would expect the worn groove to
be non-uniform and without sharply-defined edges.  If the
edges were well-defined, it suggests they were meant to be
there.  I don't suppose the manual is any help...

What was the diameter of the raised bit?  If small, it might
just be to register against a recess in the impeller's hub.

If larger, it might have been equal to the inside diameter
of the pump body's chamber, e.g. to compensate for the
thickness of any gasket.

How much thickness are we talking about here?  Could it be that
your grinding *created* the problem of this internal leak, by
making the pump chamber too wide for the impeller?

Hmm.  Now you'll have to buy a new impeller *and* a new plate.
Might as well just buy a complete new pump.  :-(

On Thu, 11 Sep 2008 14:20:54 GMT, Ronald Raygun <no.spam@localhost.localdomain>
wrote:

>John Seager wrote:
>
>> Regarding the cover plate: is it supposed to be completely flat or should
>> there be a slightly raised disc in the middle? I had assumed that the
>> raised disc was because the rest of the plate was worn, and therefore
>> ground it flat, but I suppose it might have been there from new. In
>> section, mine looked like this (greatly exaggerated):
>> _______=======________
>> _______________________
>> 
>> and is now, more or less, flat.
>> _______________________
>> _______________________
>
>If this was caused by wear, would you not have expected the plate
>to look as follows?
>
>===_____=======_____===
>_______________________
>
>That is to say that the unworn parts would be both in the middle
>where there would be less rubbing from the impeller, and also
>around the rim where the plate mates with pump's flange?
>
>Also, in the case of wear you would expect the worn groove to
>be non-uniform and without sharply-defined edges.  If the
>edges were well-defined, it suggests they were meant to be
>there.  I don't suppose the manual is any help...
>
>What was the diameter of the raised bit?  If small, it might
>just be to register against a recess in the impeller's hub.
>
>If larger, it might have been equal to the inside diameter
>of the pump body's chamber, e.g. to compensate for the
>thickness of any gasket.
>
>How much thickness are we talking about here?  Could it be that
>your grinding *created* the problem of this internal leak, by
>making the pump chamber too wide for the impeller?

In the workshop manual the cover is a normal flat disk with 6 screws holes.

>
>Hmm.  Now you'll have to buy a new impeller *and* a new plate.
>Might as well just buy a complete new pump.  :-(

John could buy one of those impeller pump covers attached with screws with
knurled heads rather than normal screws. http://www.speedseal.com/speedseal.html

John note that the cover is a flat disk.
-- 

Martin

In message , Martin 
<me@address.invalid> writes
>On Thu, 11 Sep 2008 14:20:54 GMT, Ronald Raygun <no.spam@localhost.localdomain>
>wrote:
>
>>John Seager wrote:
>>
>>> Regarding the cover plate: is it supposed to be completely flat or should
>>> there be a slightly raised disc in the middle? I had assumed that the
>>> raised disc was because the rest of the plate was worn, and therefore
>>> ground it flat, but I suppose it might have been there from new. In
>>> section, mine looked like this (greatly exaggerated):
>>> _______=======________
>>> _______________________
>>>
>>> and is now, more or less, flat.
>>> _______________________
>>> _______________________
>>
>>If this was caused by wear, would you not have expected the plate
>>to look as follows?
>>
>>===_____=======_____===
>>_______________________
>>
>>That is to say that the unworn parts would be both in the middle
>>where there would be less rubbing from the impeller, and also
>>around the rim where the plate mates with pump's flange?
>>
>>Also, in the case of wear you would expect the worn groove to
>>be non-uniform and without sharply-defined edges.  If the
>>edges were well-defined, it suggests they were meant to be
>>there.  I don't suppose the manual is any help...
>>
>>What was the diameter of the raised bit?  If small, it might
>>just be to register against a recess in the impeller's hub.
>>
>>If larger, it might have been equal to the inside diameter
>>of the pump body's chamber, e.g. to compensate for the
>>thickness of any gasket.
>>
>>How much thickness are we talking about here?  Could it be that
>>your grinding *created* the problem of this internal leak, by
>>making the pump chamber too wide for the impeller?
>
>In the workshop manual the cover is a normal flat disk with 6 screws holes.
>
>>
>>Hmm.  Now you'll have to buy a new impeller *and* a new plate.
>>Might as well just buy a complete new pump.  :-(
>
>John could buy one of those impeller pump covers attached with screws with
>knurled heads rather than normal screws. 
>http://www.speedseal.com/speedseal.html
>
>John note that the cover is a flat disk.

I have used a Speedseal - excellent bit of kit and extremely well 
engineered. I suggest that you get one and try it. I am sure that 
grinding down the plate was a bad move. The Speedseal will replace that 
plate, and if you find that you need to buy a new pump then the 
Speedseal will still fit it, so you have not wasted any money.

P.S. - used to own a boat with a YSE12 - lovely engines that go on 
forever.

-- 
Spike

On Thu, 11 Sep 2008 22:54:46 +0100, NotMyRealName 
wrote:

>In message , Martin 
><me@address.invalid> writes
>>On Thu, 11 Sep 2008 14:20:54 GMT, Ronald Raygun <no.spam@localhost.localdomain>
>>wrote:
>>
>>>John Seager wrote:
>>>
>>>> Regarding the cover plate: is it supposed to be completely flat or should
>>>> there be a slightly raised disc in the middle? I had assumed that the
>>>> raised disc was because the rest of the plate was worn, and therefore
>>>> ground it flat, but I suppose it might have been there from new. In
>>>> section, mine looked like this (greatly exaggerated):
>>>> _______=======________
>>>> _______________________
>>>>
>>>> and is now, more or less, flat.
>>>> _______________________
>>>> _______________________
>>>
>>>If this was caused by wear, would you not have expected the plate
>>>to look as follows?
>>>
>>>===_____=======_____===
>>>_______________________
>>>
>>>That is to say that the unworn parts would be both in the middle
>>>where there would be less rubbing from the impeller, and also
>>>around the rim where the plate mates with pump's flange?
>>>
>>>Also, in the case of wear you would expect the worn groove to
>>>be non-uniform and without sharply-defined edges.  If the
>>>edges were well-defined, it suggests they were meant to be
>>>there.  I don't suppose the manual is any help...
>>>
>>>What was the diameter of the raised bit?  If small, it might
>>>just be to register against a recess in the impeller's hub.
>>>
>>>If larger, it might have been equal to the inside diameter
>>>of the pump body's chamber, e.g. to compensate for the
>>>thickness of any gasket.
>>>
>>>How much thickness are we talking about here?  Could it be that
>>>your grinding *created* the problem of this internal leak, by
>>>making the pump chamber too wide for the impeller?
>>
>>In the workshop manual the cover is a normal flat disk with 6 screws holes.
>>
>>>
>>>Hmm.  Now you'll have to buy a new impeller *and* a new plate.
>>>Might as well just buy a complete new pump.  :-(
>>
>>John could buy one of those impeller pump covers attached with screws with
>>knurled heads rather than normal screws. 
>>http://www.speedseal.com/speedseal.html
>>
>>John note that the cover is a flat disk.
>
>I have used a Speedseal - excellent bit of kit and extremely well 
>engineered. I suggest that you get one and try it. I am sure that 
>grinding down the plate was a bad move. The Speedseal will replace that 
>plate, and if you find that you need to buy a new pump then the 
>Speedseal will still fit it, so you have not wasted any money.
>
>P.S. - used to own a boat with a YSE12 - lovely engines that go on 
>forever.

The only snags with Speedseal that  I know of is the cost of a replacement O
ring and that a Speedseal provided to PBO years ago didn't fit.
-- 

Martin

"Martin" <me@address.invalid> wrote in message 
news:jt5jc4pifdlo86rf0g3hmd2o1d58e7fpnv@4ax.com...
> On Thu, 11 Sep 2008 22:54:46 +0100, NotMyRealName 
> wrote:
>
>>In message , Martin
>><me@address.invalid> writes
>>>On Thu, 11 Sep 2008 14:20:54 GMT, Ronald Raygun 
>>><no.spam@localhost.localdomain>
>>>wrote:
>>>
>>>>John Seager wrote:
>>>>
>>>>> Regarding the cover plate: is it supposed to be completely flat or 
>>>>> should
>>>>> there be a slightly raised disc in the middle? I had assumed that the
>>>>> raised disc was because the rest of the plate was worn, and therefore
>>>>> ground it flat, but I suppose it might have been there from new. In
>>>>> section, mine looked like this (greatly exaggerated):
>>>>> _______=======________
>>>>> _______________________
>>>>>
>>>>> and is now, more or less, flat.
>>>>> _______________________
>>>>> _______________________
>>>>
>>>>If this was caused by wear, would you not have expected the plate
>>>>to look as follows?
>>>>
>>>>===_____=======_____===
>>>>_______________________
>>>>
>>>>That is to say that the unworn parts would be both in the middle
>>>>where there would be less rubbing from the impeller, and also
>>>>around the rim where the plate mates with pump's flange?
>>>>
>>>>Also, in the case of wear you would expect the worn groove to
>>>>be non-uniform and without sharply-defined edges.  If the
>>>>edges were well-defined, it suggests they were meant to be
>>>>there.  I don't suppose the manual is any help...
>>>>
>>>>What was the diameter of the raised bit?  If small, it might
>>>>just be to register against a recess in the impeller's hub.
>>>>
>>>>If larger, it might have been equal to the inside diameter
>>>>of the pump body's chamber, e.g. to compensate for the
>>>>thickness of any gasket.
>>>>
>>>>How much thickness are we talking about here?  Could it be that
>>>>your grinding *created* the problem of this internal leak, by
>>>>making the pump chamber too wide for the impeller?
>>>
>>>In the workshop manual the cover is a normal flat disk with 6 screws 
>>>holes.
>>>
>>>>
>>>>Hmm.  Now you'll have to buy a new impeller *and* a new plate.
>>>>Might as well just buy a complete new pump.  :-(
>>>
>>>John could buy one of those impeller pump covers attached with screws 
>>>with
>>>knurled heads rather than normal screws.
>>>http://www.speedseal.com/speedseal.html
>>>
>>>John note that the cover is a flat disk.
>>
>>I have used a Speedseal - excellent bit of kit and extremely well
>>engineered. I suggest that you get one and try it. I am sure that
>>grinding down the plate was a bad move. The Speedseal will replace that
>>plate, and if you find that you need to buy a new pump then the
>>Speedseal will still fit it, so you have not wasted any money.
>>
>>P.S. - used to own a boat with a YSE12 - lovely engines that go on
>>forever.
>
> The only snags with Speedseal that  I know of is the cost of a replacement 
> O
> ring and that a Speedseal provided to PBO years ago didn't fit.
> -- 
>
It will almost certainly be an O ring of standard size which should be 
(very) cheaply available from any worthwhile engineers' merchant.

Keith

On Sep 10, 2:29 pm, "John Seager"  wrote:
> "Norbert Koster"  wrote in message
>
> news:48c58c5e$0$185$e4fe514c@news.xs4all.nl...
>
> > John Seager wrote:
> > Try to check the sealing of the pump also. You mustn't be able to blow air
> > through the pump. If that does occur you have too much play in the pump
> > housing and you either need to replace the shaft sealing (drips water) or
> > the cover plate of the pump (too much worn).
>
> Regarding the cover plate: is it supposed to be completely flat or should
> there be a slightly raised disc in the middle? I had assumed that the raised
> disc was because the rest of the plate was worn, and therefore ground it
> flat, but I suppose it might have been there from new. In section, mine
> looked like this (greatly exaggerated):
> _______=======________
> _______________________
>
> and is now, more or less, flat.
> _______________________
> _______________________

The cover plate on my YSM8 is supposed to be flat, but where the
impeller has been spinning it has worn the plate a tiny fraction. But
the wear does not effect its ability to seal, or at least I have never
had problems sealing the cover plate, my sealing problems have always
been around the shaft.

"Martin" <me@address.invalid> wrote in message 
news:54jfc414ijqnd7pv69fjcvht9j8nvjgn9u@4ax.com...
> On Wed, 10 Sep 2008 13:48:10 +0200, "John Seager" 
> 
> wrote:
>> I guess you checked the oil level to make sure the water isn't finding 
>> it's way
> into the sump?
Now there's a cheerful thought! I don't think it is, but that's one more 
thing to check.

"LeeShore"  wrote in message 
news:2a798e69-4404-4916-a014-d6c3cd18e4b7@l43g2000hsh.googlegroups.com...
>
> Regarding the cover plate: is it supposed to be completely flat or should
> there be a slightly raised disc in the middle? I had assumed that the 
> raised
> disc was because the rest of the plate was worn, and therefore ground it
> flat, but I suppose it might have been there from new. In section, mine
> looked like this (greatly exaggerated):
> _______=======________
> _______________________
>
> and is now, more or less, flat.
> _______________________
> _______________________

>The cover plate on my YSM8 is supposed to be flat, but where the
>impeller has been spinning it has worn the plate a tiny fraction. But
>the wear does not effect its ability to seal, or at least I have never
>had problems sealing the cover plate, my sealing problems have always
>been around the shaft.

Good news! Went down to the boat yesterday and did the various tests 
suggested. Pump is pumping and not leaking, although probably not at full 
efficiency. Then I found that the elbow where the water enters the exhaust 
was almost completely blocked - a mixture of carbon, rust and whatever. 
Cleaned this out and hey presto, water coming out the exhaust again! I'm 
still going to put a new impeller in and will also check the thickness of 
the cam. John Skewes at Cellar Marine advised me that these also get worn 
down and reduce the efficiency.

Thanks again to all the posters who have given such comprehensive insights 
into the workings of this simple little pump.
John.

In message , John Seager 
 writes
>
>"LeeShore"  wrote in message
>news:2a798e69-4404-4916-a014-d6c3cd18e4b7@l43g2000hsh.googlegroups.com...
>>
>> Regarding the cover plate: is it supposed to be completely flat or should
>> there be a slightly raised disc in the middle? I had assumed that the
>> raised
>> disc was because the rest of the plate was worn, and therefore ground it
>> flat, but I suppose it might have been there from new. In section, mine
>> looked like this (greatly exaggerated):
>> _______=======________
>> _______________________
>>
>> and is now, more or less, flat.
>> _______________________
>> _______________________
>
>>The cover plate on my YSM8 is supposed to be flat, but where the
>>impeller has been spinning it has worn the plate a tiny fraction. But
>>the wear does not effect its ability to seal, or at least I have never
>>had problems sealing the cover plate, my sealing problems have always
>>been around the shaft.
>
>Good news! Went down to the boat yesterday and did the various tests
>suggested. Pump is pumping and not leaking, although probably not at full
>efficiency. Then I found that the elbow where the water enters the exhaust
>was almost completely blocked - a mixture of carbon, rust and whatever.
>Cleaned this out and hey presto, water coming out the exhaust again! I'm
>still going to put a new impeller in and will also check the thickness of
>the cam. John Skewes at Cellar Marine advised me that these also get worn
>down and reduce the efficiency.
>
>Thanks again to all the posters who have given such comprehensive insights
>into the workings of this simple little pump.
>John.
>
>
I would certainly check out your (rubber) exhaust, John.. if there's 
been a lack of water to cool the gases (as it appears) it could most 
certainly have laminated.
-- 
Keith                   replace nospam with ilf0rd

"John Seager"  wrote in message 
news:opidnY4N8uIHZlDVnZ2dneKdnZydnZ2d@saix.net...
>
> "Martin" <me@address.invalid> wrote in message 
> news:54jfc414ijqnd7pv69fjcvht9j8nvjgn9u@4ax.com...
>> On Wed, 10 Sep 2008 13:48:10 +0200, "John Seager" 
>> 
>> wrote:
>>> I guess you checked the oil level to make sure the water isn't finding 
>>> it's way
>> into the sump?
> Now there's a cheerful thought! I don't think it is, but that's one more 
> thing to check.
>
>

Over the years I have often heard about problems with the cooling pumps 
fitted to auxilliary engines in yachts.   It seems astonishing these days 
that such an apparently simple but vital item does not appear to be designed 
and manufactured to be as foolproof and reliable as possible.  Maybe there 
is good after-sales revenue for pumps exhaust bends etc.

I resorted to sourcing viton seals with stainless steel for the new pump 
shaft I turned when I discovered the standard seals appeared to be fitted 
with ferrous springs. The polymer impellor is still vulnerable to dry 
running if there is a blockage or I forget to turn on the seacock so why 
isn't there some simple reservoir and recirculation from outlet to inlet to 
prevent dry running as found in some commercial pumps?

ChrisR