Yanmar 1GM water pump

[Ron Vanderveer]

TroopsWe need to do some maintenance on our Yanmar 1GM in our Hunter 27 (have a small leak now, and besides it's been two years since we did anything to the water pump). But to us, it appears that the alternator pulley is in the way of getting the water pump off. Do we have to pull that pulley off the crankshaft in order to replace the impeller? What about to reseat or replace the entire pump assembly? If no, any tips or tricks? If yes, any tips or tricks? Thanks in advance.Ron Vanderveer

 

[Bill O'Donovan]

If it's like the 2GM...

...you simply remove the bolts behind the pulley. These fasten the water pump to the engine. Then you turn it over and remove the small bolts for the impeller. Make a mental note of the pully tension so as to replicate it when you reassemble. This reads more complicated than it really is. To answer your fundamental question, the fanbelt will come off as you dismantle the water pump. Not to worry.

 

[Terry]

Hi Ron, I replaced the raw water impeller...

and seal on our 2GM without removing the crank pulley. I'm assuming that it is your raw water pump that is dripping indicating that the seal is worn out. I replaced the seal and impeller on ours, no big deal with the right tools. A new 2GM pump would have cost me like $250 whereas the rebuild kit was $60 if I remember right. Whether the 1GM is that much different than the 2GM, someone else maybe can weigh in with more advice. I bought the rebuild kit from the local Yanmar service shop and he showed me the right way to do the job. Oddly the kit did not come with instructions.Terry

 

[John Lynch]

2 GM(F) Water pump rebuild- Mushroom

I just rebuilt my water pump- Mushroom Laws in effect. 1) Replace the impeller & gasket. Still leaks!2) Call Torrenson Marine( First of 3 times) These folks are the best!!!!!Tapped the impeller shaft out and discovered that broken oil seal ring had allowed water to rust 1 of the 2 ball bearings. Ordered 2 ball bearings $7.00 apiece.3) Tried unsuccessfully to remove damaged ball bearings from imp. shaft. Damaged the shaft! Call Torr and layout $95.00 for new shaft & V pulley.4) Re-assembled! Keep in mind that the oil seal ring needed to be jymmied into place at the 2 vents with a flat head as assembly did not have it in its optimum position.2 things to noteMACHINE PRESSThe guys at my marina had a press: no other way to replace ball bearings.Period.CIRCLIPThere is a circlip between the 2 ball bearings. It is not shown on the Yanmar manual. Luckily, I was able to salvage it from the old shaft.I am now a water pump expert and even though what I thought was a quick fix became an endurance test, it was fun to solve.I mention about the press because small leak & no maintainence > 2 years, that ball bearing is not gonna be fun or wanna let go from the shaft.To remove the pump, undo the 2 long bolts which suspend the pump away from teh engine and then loosen V-pulley lock nut: Then, the fun begins!Good Sailing!s/v LOTUS