Yanmar 2GM20F raw water pump

[wannacat]

Thanks Wotname for this! Yes I'm aware there's a Euro and Japanese model. I believe it's just the bracket that's a little different for some reason? My dealer got it wrong one time for me as you mentioned can happen. I installed it as initially it looked the same, but once on, the pulley was out of alignment by half it's width.

[bratzcpa]

Originally Posted by jimbunyard

I keep seeing F4B903. You might call these people to verify.

Yanmar 128397-42500 Engine Cooling Pump Bronze

What Jim bunyard said! I have a 3GM30 in a Catalina 320. I used this company and ordered this exact pump. They are located in Florida. I was disabled and "stuck". Their shipping was same day - super fast. This was a perfect replacement for me.

I also ordered the rebuild kit and rebuilt the old pump . . . and now keep that for my spare.

[wannacat]

Just got an email back from Pumpvendor.com. They will only reference the Yanmar part # and stated that yes it's a Johnson but made only for Yanmar and sold only as Yanmar in the $600 range! So maybe I'll take a chance on the Johnson one you mentioned? Mine does have bolts not screws on the faceplate, don't know what internal differences if any? Would need a metric micrometer to really sort things out and I have one but back home in the great white north. I'll keep digging and see who else might respond with a definite number for a Johnson replacement. Thanks again!

[bratzcpa]

Originally Posted by wannacat

Just got an email back from Pumpvendor.com. They will only reference the Yanmar part # and stated that yes it's a Johnson but made only for Yanmar and sold only as Yanmar in the $600 range! So maybe I'll take a chance on the Johnson one you mentioned? Mine does have bolts not screws on the faceplate, don't know what internal differences if any? Would need a metric micrometer to really sort things out and I have one but back home in the great white north. I'll keep digging and see who else might respond with a definite number for a Johnson replacement. Thanks again!

Yep, the bolts on the plate hold down are a definite improvement . . . . from the phillips head on the original. Much easier to get a small box end wrench on it.

I actually went one step further, and ordered stainless steel wing screws (not sure that's really what they are called). They are threaded screws, but have "wings", kind of like a wing nut. It allows for a quick and easy check/changeover of the impeller.

[billgewater]

I purchased a new Yanmar 1 GM at a liquidation sale many years ago and decided to use it as a gen. set etc. I removed the gear box and installed a lay shaft to run various compressors and a 240 VAC alternator (some issues with auto regulation). I also installed an independent water pump from a local supplier.and sealed off the Yanmar pump hole. The new pump, with a spare impeller cost less than a single Yanmar impeller for the engine mounted Yanmar pump. In twenty or more years I have not had to replace the impeller. So my suggestion is to have a look and see if you can arrange the mounting of a separate pump. A consideration is that should the shaft seal fail on your Yanmar pump, salt water may ingress to the sump oil. Now that could be an expensive event. Another advantage is that a larger pump can be installed allowing raw water for use in (as an e.g.) a refrigeration condenser or even a back up bilge pump. The only advantage I can see with the Yammar engine water pump is that it is compact.
The little Yanmar has given excellent service except for two occasions. One when the single piston developed a crack which really was an expensive event and when the exhaust corroded. I replaced the copper based exhaust with a fabricated SS one using off the shelf components. Larger, heavier. Yes. Bullet proof. Yes. Cheaper. Yes.

[DotDun]

Originally Posted by billgewater

I purchased a new Yanmar 1 GM at a liquidation sale many years ago and decided to use it as a gen. set etc. I removed the gear box and installed a lay shaft to run various compressors and a 240 VAC alternator (some issues with auto regulation). I also installed an independent water pump from a local supplier.and sealed off the Yanmar pump hole. The new pump, with a spare impeller cost less than a single Yanmar impeller for the engine mounted Yanmar pump. In twenty or more years I have not had to replace the impeller. So my suggestion is to have a look and see if you can arrange the mounting of a separate pump. A consideration is that should the shaft seal fail on your Yanmar pump, salt water may ingress to the sump oil. Now that could be an expensive event. Another advantage is that a larger pump can be installed allowing raw water for use in (as an e.g.) a refrigeration condenser or even a back up bilge pump. The only advantage I can see with the Yammar engine water pump is that it is compact.
The little Yanmar has given excellent service except for two occasions. One when the single piston developed a crack which really was an expensive event and when the exhaust corroded. I replaced the copper based exhaust with a fabricated SS one using off the shelf components. Larger, heavier. Yes. Bullet proof. Yes. Cheaper. Yes.

"and sealed off the Yanmar pump hole."
What does that mean? Yanmar GM series raw water pumps are external, there is no 'pump hole'.

'may ingress to the sump oil'
Makes no sense!

??

[DotDun]

Originally Posted by wannacat

Thanks Wotname for this! Yes I'm aware there's a Euro and Japanese model. I believe it's just the bracket that's a little different for some reason? My dealer got it wrong one time for me as you mentioned can happen. I installed it as initially it looked the same, but once on, the pulley was out of alignment by half it's width.

Which one do you have?

[Wotname]

Originally Posted by wannacat

Thanks Wotname for this! Yes I'm aware there's a Euro and Japanese model. I believe it's just the bracket that's a little different for some reason? My dealer got it wrong one time for me as you mentioned can happen. I installed it as initially it looked the same, but once on, the pulley was out of alignment by half it's width.

I can't speak to your engine but my 2GM20 (with an E serial number) (and not a 2GM20F) had other differences re the RW pump when compared to the same year build non E serial number: impeller size and pump outlet hose diameter and shape.

Interesting to hear of the bracket shape; all part of the fun of maintaining boat stuff

[billgewater]

Dear Dotdun.
My Yanmar is a 1 GM and it most definitely did have a raw water pump that was mounted on the front of the engine block and had a shaft that went inside the engine block. (It used a 21 mm impeller). But you are correct re the 2 GM. It's raw water pump is bracket mounted - see P 17 of the Yanmar manual. On page 25 it shows a 1 GM without the bracket plate, pump and extra belt. I guess that having the external mounting plate may still allow an owner to consider an alternative pump.

[RaymondR]

When I needed to replace the pump on my 3GM30 I was quoted about $850 Australian for a genuine Yanmar replacement. The same sized Johnston pedestal mounting pump was less than $300.

I used a piece of unequal angle alloy section to make a new mounting plate, bolted the pedestal pump to it and it is still on the engine about ten years later.

In addition to the much lesser cost the alloy plate does not go rusty as did the original Yanmar steel mounting.

[jimbunyard]

Originally Posted by wannacat

Just got an email back from Pumpvendor.com. They will only reference the Yanmar part # and stated that yes it's a Johnson but made only for Yanmar and sold only as Yanmar in the $600 range! So maybe I'll take a chance on the Johnson one you mentioned? Mine does have bolts not screws on the faceplate, don't know what internal differences if any? Would need a metric micrometer to really sort things out and I have one but back home in the great white north. I'll keep digging and see who else might respond with a definite number for a Johnson replacement. Thanks again!

This is a common topic; what some see as 'price-gouging', others see as 'the manufacturers right to ensure their profitability'. All manufacturers due it to some extent; to me it seems Yanmar and Volvo are among the worst...

Here is a picture of the Yanmar part, per P/N 721575-42702. Note the 2 different brackets provided.



Here is a dimensional drawing of a Yanmar p/n 128397-42500, which is an F4B903 or 902.




Since you have a pump, you can measure yours and compare it to the drawing to see if they are externally dimensionally compatible.

If they are, that still leaves the question of suitability for your application.

They are not the same internally, the 721575-42702 has a key driven, 50.8 mm dia x 22.1 thick x 12.7 shaft impeller, while the 128397-42500 has a pin driven, 40 x 19 x 12 impeller.

This doesn't mean it won't work, just that it's different.


I have seen the same thing with Volvo engines, where engines identical in every other way have different raw water pumps, in my particular case because the pumps were made by different companies, Jabsco and Johnson. I wonder if the same thing is going on here.

[RaymondR]

The thing of it is that it's a bolt on item which serves a very imprecise function and provided the engine gets sufficient cooling water it does not matter how it is done.

As an emergency backup I carried a 12V electric impeller pump, which I used on a number of occasions when the engine mounted pump failed, without any problems.

I also had philosophical problems with the exhorbitant cost of the alternator and modified the mounting so that I was able to use a Bosch universal 85 anmp alternator which was about 1/3 the cost of a genuine Yanmar part.

Some of us just delight in occasionally beating the extortionate systems certain folks use to exploit us. There is absolutely no functional or even aesthetic reason why Yanmar has to use a "special" mounting on this item rather than one which would allow the use of a cheaper pump.

[DotDun]

Originally Posted by billgewater

Dear Dotdun.
My Yanmar is a 1 GM and it most definitely did have a raw water pump that was mounted on the front of the engine block and had a shaft that went inside the engine block. (It used a 21 mm impeller). But you are correct re the 2 GM. It's raw water pump is bracket mounted - see P 17 of the Yanmar manual. On page 25 it shows a 1 GM without the bracket plate, pump and extra belt. I guess that having the external mounting plate may still allow an owner to consider an alternative pump.

You are correct! I learned something today! I had to look in my service manual to see what that beast looks like! It is a cute little pump......

[wannacat]

So I've taken the pump apart and it is the Japanese model with the keyed shaft. There's a Johnson # on the impeller -#827. The seal is a NOK - AE0478A 18,
The 2 bearings are both NACHI - 6202ZE.
Which way do the bearings come off? Towards the impeller end or the pulley end.
The shaft measures the same dia. on each side. I don't know what keeps them in place? You'd think one side would be necked down or have a retaining clip? Also, somewhere I seen the blow up of the Yanmar parts for this pump and now can't find it? Anybody have one?

[jimbunyard]

6202's are probably one of the most common small machine bearings you'll find, get both the seal and brgs from the local brg house, as advised previously. According to the drawing below there should be two rings locating the bearings, if you don't have them, take the shaft with you to the brg supplier...

If the shaft is the same size,the bearings can come off either way; a 3/8"/10 mm socket and a piece of 1/2" water pipe (rides on the inner race of the bearing), a block of wood and a hammer come in handy here...