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Discussion Starter · #1 · (Edited)
The water pump on my raw water cooled Yanmar 2GM20 Water is leaking. It drips for about an hour after I shut the motor down (I assume until it drains the water in the line). This is the best picture I could get of the bottom of the pump. It seems like the water is coming from the hole in the picture. Any ideas what might be causing it before I tear it apart?
 

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Swansea, MA
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The shaft seal is bad, and needs to be replaced. I had it happen to mine a couple of years ago, replaced both bearings and the seal, very easy to do. I have 2GMF. Mine was leaking when the motor was running but it was the exact same spot.

Good luck,

Pat
 

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It's a weep hole. There are two seals in that pump: An outer one to keep water out of the engine and an inner one to keep oil in the engine. That weep hole is between the two. You need new seals. Btw: Don Moyer (Moyer Marine) recommends you put a bit of sealant around the seat of the "outside" seal before installing it, so any minor dings or imperfections in the seal's seat doesn't leave you with water still dribbling out (as happened to me).

And note carefully that the seals go in a certain way: With the stamped lettering on them facing one another.

Jim
 

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The shaft seal is bad, and needs to be replaced. I had it happen to mine a couple of years ago, replaced both bearings and the seal, very easy to do. I have 2GMF. Mine was leaking when the motor was running but it was the exact same spot.

Good luck,

Pat
I agree. I'll just add that the hole at the bottom is a weep hole, through which any water leaking from a bad seal will pass.

Another thing: One winter, I forgot to loosen the water pump belt when I winterized our previous 2GM20F. This caused the shaft to sit with uneven tension for the entire winter (4+ months). In the spring, the shaft seal was distorted and it leaked a bit. I was going to replace it, but after using the engine a few hours (probably 10+), the seal seemed to get back in proper shape and it stopped dripping and never dripped again.

So if your boat has sat for quite a while with tension on the water pump belt, try running the engine a bit and see if the seal will reseat itself. If not, it's probably time for a new one.
 

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Discussion Starter · #6 ·
The shaft seal is bad, and needs to be replaced. I had it happen to mine a couple of years ago, replaced both bearings and the seal, very easy to do. I have 2GMF. Mine was leaking when the motor was running but it was the exact same spot.

Good luck,

Pat
Thanks everybody! I'm sure mine is leaking while it's running also, I just can't hear it. The Yanmar manual doesn't give me much. I assume when I pull it apart it will be fairly self explanatory? Thanks again!
 

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Swansea, MA
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it is actually very simple to rebuild, especially since you can pull the pump off in about 10 minutes and bring home to rebuild. I forget how much the seals and bearings were but I used Torresen for the parts. I ended up stripping and painting the pump / pulley while I was at it.

Marine Diesel Engines and Engine Parts from Torresen Marine's Marine Diesel Direct - Universal - Volvo - Westerbeke - Yanmar - MASE

I actually keep a spare pump on board, so I put in the spare, and rebuilt the leaking one for the new spare. (mechanical engineer so I am a little excessive compulsive)

Pat
 

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Discussion Starter · #8 ·
I got the parts from the local Yanmar dealer. Strange thing is, the parts diagram (see picture) calls for 2 bearings (#7) and 1 oil seal (#8). No water seal. The motor is a 2GM20(F). I questioned the lady at Yanmar about it and she showed me the diagram (which she had nicely copied for me) and correctly said "your looking at the same thing I am". This makes me wonder, what keeps the water in the pump, and if I don't have a water seal, whats leaking? I could pull it apart, but have a race coming up and don't want to unable to get a part. Ideas?
 

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I got the parts from the local Yanmar dealer. Strange thing is, the parts diagram (see picture) calls for 2 bearings (#7) and 1 oil seal (#8). No water seal. The motor is a 2GM20(F). I questioned the lady at Yanmar about it and she showed me the diagram (which she had nicely copied for me) and correctly said "your looking at the same thing I am". This makes me wonder, what keeps the water in the pump, and if I don't have a water seal, whats leaking? I could pull it apart, but have a race coming up and don't want to unable to get a part. Ideas?
Your pump is belt driven not engine driven therefore you only need one seal. That seal is for raw salt water or lake water. On some engines the pump bolts directly to the engine block where it is splash lubed by oil and driven directly off the engine so you'd have two seals one for water and one for the oil side.. Yours is driven by a belt thus one seal...
 

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Discussion Starter · #10 ·
Your pump is belt driven not engine driven therefore you only need one seal. That seal is for raw salt water or lake water. On some engines the pump bolts directly to the engine block where it is splash lubed by oil and driven directly off the engine so you'd have two seals one for water and one for the oil side.. Yours is driven by a belt thus one seal...
So...should it be dripping water?
 

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I just service the raw water cooling pump of my 2GM20F. The oil seal serves as water seal. There's another water seal which is an O-ring that is located between the oil seal and the bearing. This water seal (O-ring, number 10) can be seen at the "window". In front of the bearing there is a washer (16). All you probably need is the oil seal, water seal and perhaps the 2 bearings IF leak water do get as far as the bearing. You going to push out the bearings and shaft assembly so might as well replace the bearings. Should you remove the bearings, you should polish up the shaft. What I did is bring the oil seal, water seal, bearings, C-clips to a bearing specialist who supply me all this at non marine price. Just couple of dollars for all. I've written a Work Instruction on this repair. Give me your email address if you're interest in this WI.
Seawater Pump, Oil Seal p/n: 12x24x7-TC-NOK S$1.30 +gst
Seawater Pump, Water Seal O-Ring p/n: P12-OR-KHS S$0.10 +gst
Seawater Pump, Bearing p/n: 6201-LLU-NTN S$2.60 +gst
Seawater Pump, Bearing p/n: 6201-JRXLLU-NTN S$2.60 +gst
Seawater Pump, Circlip small p/n: A12-CIRCLIP-ADT S$0.30 +gst
Seawater Pump, Circlip big p/n: B32-CIRCLIP-ADT S$0.50 +gst

BTW, No it should not be dripping water. When pump is good its dry as a bone on the outside.

Cheers!
 

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But...

Halekai (now Maine) --

How is it that every photo you post is of equipment in pristine and squeaky clean condition?
cheers
pegasus
It looked like this when I started..;)


Does everything on your boats look like that?
Not everything but I do like to keep it in good shape..:)

Engine at 2900 hours...
 

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Discussion Starter · #15 · (Edited)
Bearings were almost frozen!

I took the pump apart and couldn't pound the bearings off the shaft. I finally destroyed the bearings just to see what was holding them on. It appeared to me that the bearing race is part of the shaft (see picture). Sent the picture to the Yanmar dealer and he assured me the bearings were frozen on the shaft (hard to believe looking at them closely), and that I need a new shaft. Salt water had definitely penetrated the bearings and they were hardly turning at all (wonder how long they've been like that)! Amazingly, they did loosen up with some WD. I've had the boat three years and have never thought I had sufficient flow, but didn't overheat. Amazing! Just think....my impellers almost brand new! :laugher Of course...I should probably replace the belt (surprized I didn't smell it!) :mad: BTW, "Trantor" sent me his instructions for servicing the pump. Most service manual writters would be envious! Nice job Trantor, and thanks!
 

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Discussion Starter · #16 ·
Took the shaft to the Yanmar shop and they used a press to remove the bearings (races), and the shaft looked good (to my surprise). Don't know how everyone else was able to remove them without a press, but there was no way I was going to be able to do it!
 

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Discussion Starter · #17 ·
oops!

Believe it or not, I'm still working on this pump (parts delay). When I removed the seal, it was very worn. I thought part of it remained in the front of the housing and started digging it out. I'm having a difficult time removing it, and think the rubber piece I'm removing is part of the housing:eek: If so, I just bought myself a new pump! It never occurred to me that the housing might have a seal that didn't get replaced. Did your pump have a piece of rubber in the housing that remained, or is that part of the old seal (right answer:) )? If so, how did you get it out?
 

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If you're referring to the rubber oil-seal, refer to step 13 of "Dis-assemble the Pump". There are no special tools required for rebuilding of the Johnson water pump. All tools used are common to an DIY'er. Socket spanner can be double as a cylinder press if use with a suitably size vice.
 

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l124c the water seal is a B%^&% to get out, mine was so gone that i thought it was perminate. you need to drive it out with a round dowel or some thing, just work you way around it while hitting it with a small hammer. if it gets c0cked in the hole it wont move
 

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Discussion Starter · #20 · (Edited)
For the record, the rubber I was worried about was part of the old seal. There are no rubber pieces that are part of the pump housing. Whew!!! The pump is over $400! Oh, and I did need to replace the shaft. It had what I thought was minor scoring, but Yanmar convinced me it would probably still leak, if not replaced.
 
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