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Old 29-03-2018, 14:49   #31
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Re: Yanmar 2GM20F raw water pump

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Originally Posted by wannacat View Post
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?
I don't have the exact pump but I understand the bearing will come off towards the pulley end (normal practice). In part this is because you don't want to sliding the interference fit of the bearings over the surface of the shaft which must remain polished and blemish free. Forcing a bearing over that section is bad practice.

FWIW, those bearing are common and as you probably know by now, they are readily available. Just ask for 15mm (ID) x 35 mm (OD) x 11 mm (deep) shielded ball bearing.

The seal maybe slightly more difficult. While is fairly common to get an oil seal of that size (13mm ID x 28 mm OD x 7 mm deep), your seal has (or should have) a SS spring just inside the seal lip. Common oil seals will have a carbon steel spring rather than a SS one. Clearly the SS is better than carbon steel when sealing sea water. However there is a simple fix if all you can get is an oil seal with a carbon steel spring.

Pop the spring out and replace it with an appropriately sized O ring i.e. an O ring that provides some compressive force on the lip of the seal similar to the spring.

If buying in person, take a small magnet with you to check the spring composition or just get an O ring to suit at the same time. I have been replacing the springs with O rings for years without any issues for seals used in sea water applications.

EDIT: I note Jim was posting at the same time
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Old 29-03-2018, 15:04   #32
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Re: Yanmar 2GM20F raw water pump

Just noticed another difference between the 721575-42702, and the F4B903; there are no weep slots on the former.

That means that if the single seal goes bad, the water goes through the shields on the 6202ZE bearings and into the boat. 6202DD sealed bearings might be a better choice here, ask for an opinion at the bearing house...
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Old 29-03-2018, 15:11   #33
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Re: Yanmar 2GM20F raw water pump

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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
This surprises me, as I understood that the 2GM & 3GM motors used the same pump? We have a 3GM30F and currently have both European & a Rest of the World pumps fitted/in the spares locker and other than the different impellors the pumps as a whole (including the brackets) and their individual parts have proved directly interchangeable.
I recall that when we were in the US, the Johnson E Version was about $150-200 cheaper than their rest of the world model, however I'm told that in Europe, Johnson will/do not sell the E-Pump at all it is only available through Yanmar
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Old 29-03-2018, 15:28   #34
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Re: Yanmar 2GM20F raw water pump

Thanks Jim! That was the exact diagram I was looking for! One thing I notice is there's a cir clip it appears between the 2 bearing according to the diagram and the shaft looks to be slotted to accept it? If so then 1 bearing at a time must be pushed [pulled ] off , then remove the snap ring and bring the other bearing off the same way so as not to score the shaft where the seal goes as mentioned by "wotname". I can't tell if there is one between them or not ? But will try pulling one at a time tomorrow. Thanks again to both of you guys!!!!! You've been very helpful!!!
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Old 29-03-2018, 15:43   #35
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Re: Yanmar 2GM20F raw water pump

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...........
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...

..........
For the OP who I understand is "learning the trade" about pumps etc, the highlighted part of Jim's excellent post is important.

One should apply force to the race that is in contact with fitting surface i.e. the inner race when fitting to a shaft and the outer race when fitting to an housing.

Not so important when removing and discarding an old bearing but important when fitting new (or existing) bearing.

If not done this way, then the force is transmitted via the balls etc in the bearing and can cause (usually slight) damage to the balls and races.

I apologise in advance if you already know this!
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Old 29-03-2018, 23:41   #36
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Re: Yanmar 2GM20F raw water pump

Opps... belay my last post (#35); I got this OP mixed up with another OP of another raw water pump thread.
My bad.

This is no reason to suppose the OP of this thread is not already full bottle on water pump repairs so please accept my apology to think otherwise.
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Old 31-03-2018, 05:53   #37
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Re: Yanmar 2GM20F raw water pump

No problem Wotname! Yes I do have the experience to deal with this type of problem but there probably might be others following the thread who don't, so every little detail helps others and we all had to learn from someone at one time.
So the local Johnson dealer couldn't match the pump yesterday. Next week I'm off to a local bearing supply house and will piecemeal the thing myself.
Thanks to all for your help with this matter.
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Old 31-03-2018, 10:29   #38
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Re: Yanmar 2GM20F raw water pump

Have not read thru entire thread, but hoping this will help OP.
Years ago I replaces my raw water pump on my 3gm (raw water motor 22.5 hp)
with Johnson pump F4B-903 from Depco in Fl. (which uses impeller #810B-1 pin driven
with 5/8" hose in/out)
I also am very familiar with 2 friends 2GM20F European motors as I do all maintenance on one, and their pumps "seem" identical to mine using same impeller and same output.
At the time of my purchase Depco gave me comfort indicating they would take pump back if any problem. No need as all was good. Price was about half, in mid 200.'s, of
replacing my Japanese original pump.
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Old 04-04-2018, 19:56   #39
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Re: Yanmar 2GM20F raw water pump

Well after hunting around I was only able to by the bearings at a supplier. He didn't have the lip seal and stated probably no one else around would either as it is 13mm. Definitely no SS spring available either. So I ordered the seal and impeller from Yanmar. Put it all together today and it runs fine with no leaks. I would have possibly gone with the Johnson F4B-903 but couldn't get my hands on one directly to make sure of things. Plus I don't want to have to change the other one over and buy an extra backup so decided to stay with the OEM stuff for now. Also the boat is up for sale and don't want the next owner all screwed up with 2 different types of pumps and parts. Didn't cost me much to do the rebuild so all is good for now.
I would like to thank everyone who tried to help out with this thread!!! Much appreciated and hopefully others have learned something also!
Cheers!
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