Yanmar raw water pump

pete

pete

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I have been having trouble with my Yanmar 2GM20F(2002 model) Johnson raw water pump struggling to prime for the last 2 years. After replacing impeller twice ,fitting a new speed seal with Teflon disk, and rerouteing the pipework and strainer I have finally decided to replace the pump.
When winterising the engine today with the pump sucking from a bucket with a bottom outlet around 3 foot and immediately above it you can hardly feel any suction at the water outlet in the tank.
The pipework is not blocked in any way and the complete system can be blown through easily. This pump has done around 1000 hours probably mostly in silty water.
So the question is- is there a preferred Yanmar supplier who offer better prices or are they all about the
same ?.
Best I can find so far is-- Marine Power part 128387-42500 £263.14 inc vat

Thanks
Pete
 
Not sure it is a pump problem.... I would look at air leaks on the inlet - the pump will pull air before water due to density and physics. Even a knackerred FIP, will move some water, if all the system is OK...

Johnson Pumps and Jabsco Pumps are very reliable, you have replaced everything on the pump, whether needed or not, so it has to be the system...

If the boat is in the North West, I can come and assist - would give me an excuse to see my parents!
 
I have read that wear can reduce the performance of these pumps. Pumping silty water would cause wear in 1000 hours.

Wear can occur to the end faces of the impellor and housing. The total clearance between the faces of the impellor and the inside of the housing/cover plate should be between 0.2mm and 0.4mm.

I believe that the "bump" on the inside of the pump, which bends the impellor blades and basically seals the outlet from the inlet also wears away. The bump is actually a separate piece called a cam in my Yanmar 2GM20 workshop manual. The cam is secured by a screw passing through the wall of the pump. If the cam is worn away, it will need to be replaced.

If the clearance (with a new impellor) is more than 0.4mm or if you can't get a new cam you will require a new pump.
 
jon711 and Eygthene Thanks for your replies.
There are definitely no air leak before the pump. For flushing the engine at the end of the season. I have built up a central heating header tank with a flange in the side at the bottom with the a pipe feeding directly down vertically to the pump about 3 foot below so exerting over .1 bar pressure with the tank full.
The pump was pumping with the pipe vertical but as soon as the tank was put on the cockpit floor and the pipe had to run up about 6" over the bridge deck the pump stopped sucking.
I suspect that the inner face of the pump body and the cam are worn. The cam is not removable on this pump (poor design !) I had similar problems on my last boat with a 1GM10 engine but not quite so bad. I mentioned this to a friend with the same engine at the club and he said he sometimes has trouble with priming as well so may be it is the water that we sail/motor in that is causing the trouble.
I was an heating engineer for a few years so I do appreciate what you say about air leaks though.




Thanks again
Pete
 
I had to replace my pump and did a lot of shopping around for prices, Marine Power was the cheapest price I could find for a Johnson Pump and they where excellent to deal and very helpful. I have also rebuilt the old unit as a spare using parts from Ribs Marine, they have an excellent parts portal with diagrams of most Yanmar engine parts and well worth a virtual visit, link below. Good luck.

www.ribsmarineparts.co.uk
 
Thanks Simon 054
looks like Marine power it is then. I looked at the ribs marine site (strange system) you have to register before you can use the site which I did then it looks like I would have to download MS Silverlight and use "Internet Explorer" This was a step to far. :eek:
pete
 
pete said:
I have been having trouble with my Yanmar 2GM20F(2002 model) Johnson raw water pump struggling to prime for the last 2 years. After replacing impeller twice ,fitting a new speed seal with Teflon disk, and rerouteing the pipework and strainer I have finally decided to replace the pump.
When winterising the engine today with the pump sucking from a bucket with a bottom outlet around 3 foot and immediately above it you can hardly feel any suction at the water outlet in the tank.
The pipework is not blocked in any way and the complete system can be blown through easily. This pump has done around 1000 hours probably mostly in silty water.
So the question is- is there a preferred Yanmar supplier who offer better prices or are they all about the
same ?.
Best I can find so far is-- Marine Power part 128387-42500 £263.14 inc vat

Thanks
Pete
Click to expand...
I had a similar problem with my pump. It was a yanmar and used in silty water. Exactly the same symptoms you describe. We stripped the pump and decided it was the lip seal. Some people fit two seals to resolve the issue. The s/s shaft was scored where the lip seal sits so I priced up a new shaft. £100 from dealer! I took the old shaft to a machine shop and they made me one for £30. We put it back together with a new lip seal and it was perfect. Sucked as good as new.
 
geem said:
I had a similar problem with my pump. It was a yanmar and used in silty water. Exactly the same symptoms you describe. We stripped the pump and decided it was the lip seal. Some people fit two seals to resolve the issue. The s/s shaft was scored where the lip seal sits so I priced up a new shaft. £100 from dealer! I took the old shaft to a machine shop and they made me one for £30. We put it back together with a new lip seal and it was perfect. Sucked as good as new.
Click to expand...

I would also suggest changing the shaft seal before going for a new pump. Cam wear is most definitely a potential cause of failure to prime but worn seals are another. My pump on a Yanmar 3GM30F often failed to prime after sailing in boisterous conditions, virtually from new. After many years of service the seal failed and was replaced. The pump has never failed to prime since.

Not quite sure how you could fit two seals as the housing will only accept one.
 
vyv_cox said:
I would also suggest changing the shaft seal before going for a new pump. Cam wear is most definitely a potential cause of failure to prime but worn seals are another. My pump on a Yanmar 3GM30F often failed to prime after sailing in boisterous conditions, virtually from new. After many years of service the seal failed and was replaced. The pump has never failed to prime since.

Not quite sure how you could fit two seals as the housing will only accept one.
Click to expand...

two seals involved some machining. A bit over the top if you ask me. mine never failed to prime once we replaced the shaft and put a new seal in.
incidentally, so the shaft didnt wear again we heat treated the it. I was fortunate that a pal had access to free heat treatment. it was impossible to scratch the 316 s/s shaft once it was hardened.
 
Hi geem and vyv_cox
Thanks for your reply's. I am not sure how the shaft seal can prevent it priming as I guess it would have to be allowing air into the pump and there is no sign of any water leakage but I will certainly strip the pump next weekend and inspect the shaft and seal and probably clean up the shaft give it a go with a new seal. They are not normally very expensive from my local bearing stockist (there is no big rush to buy a new pump as the boat is ashore for the winter)

Pete
 
pete,

I had similar probs, it turned out that the back of the pump housing had worn away, too many grooves, it didn't help, as still needed a new pump.

We often change the cover but never think about the back, I suppose it gets equal wear?
 
capetown said:
pete,

I had similar probs, it turned out that the back of the pump housing had worn away, too many grooves, it didn't help, as still needed a new pump.

We often change the cover but never think about the back, I suppose it gets equal wear?
Click to expand...

Thanks for that. I am assuming that is what is wrong with my pump.
If the front plate wears and it had, then the back and cam must also wear. if the cam was not permanently fixed and with nothing to loose I would probably have tried to skim the back of the pump in my lathe to remove the wear and fit a shim but with the fixed cam it is beyond my capabilities. But I will try the shaft seal before buying a new pump.
Pete
 
If the shaft is scored, a quick dodge is to fit a fibre washer behind the replacement lip seal. This moves the seal out of its housing just enough for the lip to run on a non-scored portion of the shaft.

The reason a failed lip seal can lead to failure of the pump to prime is that it allows the pump to draw air from around the shaft, rather than water up the pipes. You wouldn't see a leak as it's a suction side failure.
 
Last edited:
jon711 said:
Not sure it is a pump problem.... I would look at air leaks on the inlet - the pump will pull air before water due to density and physics. Even a knackerred FIP, will move some water, if all the system is OK...

Johnson Pumps and Jabsco Pumps are very reliable, you have replaced everything on the pump, whether needed or not, so it has to be the system...

If the boat is in the North West, I can come and assist - would give me an excuse to see my parents!
Click to expand...

Why are Jabsco so ridiculously expensive? Good quality I know but blo*dy stupid pricing policy.
 
Last edited:
Update
As a last attempt to get my raw water pump to suck I followed suggestions and bought a new shaft lipseal, about £2.60. I stripped the pump and cleaned the shaft very lightly sanding with fine wet and dry it came up like new in a few seconds. I greased the shaft and fitted the new seal I re-built the pump applying a bit of silicone grease to the recently new impeller. But I could still blow through it easily and am sure that the problem is that the rear face of the pump is worn unevenly more so at the centre under the impeller hub. I expect that if the pump body was not worn so badly replacing the lip seal would have helped.
I ordered a new pump from Marine Power yesterday for £278 delivered, it came today (very good service) and I cannot blow through this new pump.

I do wonder why they come with the bracket and pulley though, these are easily detachable and must add to the cost.

Thanks for all help and suggestions

Pete
 
pete said:
Update
As a last attempt to get my raw water pump to suck I followed suggestions and bought a new shaft lipseal, about £2.60. I stripped the pump and cleaned the shaft very lightly sanding with fine wet and dry it came up like new in a few seconds. I greased the shaft and fitted the new seal I re-built the pump applying a bit of silicone grease to the recently new impeller. But I could still blow through it easily and am sure that the problem is that the rear face of the pump is worn unevenly more so at the centre under the impeller hub. I expect that if the pump body was not worn so badly replacing the lip seal would have helped.
I ordered a new pump from Marine Power yesterday for £278 delivered, it came today (very good service) and I cannot blow through this new pump.

I do wonder why they come with the bracket and pulley though, these are easily detachable and must add to the cost.

Thanks for all help and suggestions

Pete
Click to expand...
on the engine side of the impeller chamber is a "wear plate" , remove the cam & it will come out. these are consumer items to save pump wear

http://www.asap-supplies.com/search/johnson+wear+plate
 
Last edited:
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