Minor Engine Overhaul

[Chris Behre]

I have a Yanmar YSM 12 (noisy one-lung) on my Hunter 30 (1978). I doubt it's ever been rebuilt, but is has given me relatively few problems in 8 years. I would like to do an upper end rebuild on it myself. Can anyone recommend a good do-it-yourself repair manual that goes beyond the standard water pumps, and filters level of repair?

 

[Patrick Neeley]

Yanmar

Chris, check with your local Yanmar parts supplier. They can sell you a workshop manual published by Yanmar which gives you everything you will ever need to know about your engine. My 2GM20F manual provides complete rebuild instructions, with specifications, and visual aids.

 

[Pete]

top end rebuild

Chris, the Yanmar engine manual is the best resource for a rebuild,availabe at any Yanmar dealer.I not sure if I understand why you are rebuilding the top half only,and not the complete engine and not sure why you are rebuilding any thing at all. You say it has not been rebuilt and given you only minor problems,why even rebuild it? These engines can go years and years and thousands of hours before a rebuild is needed.(unless there is a issuse of overheating or no oil type problem) I would suggest to you that if it ain't broke don't fix it !

 

[Miles]

Just to clarify...

The shop manual is great, it's not the one that comes with the engine but you can get it from a dealer. It's around $40 and well worth it.

 

[Chris Behre]

Thanks

I ordered the Yanmar manual from Torresen's Marine Diesel Direct. Pete, I USUALLY subscribe to the theory of "if it ain't broke..." but over 20 years without any major work leaves me a little nervous. I may have been too generous originally. Early last season my intake vale was sticking, but a little WD-40 quick fixed it. I also feel I have lost a bit of power over the years. I am only planning on doing the top end because I feel confident I can do that much my self (except for machining the head of course). Then again I might get in there and realize it need to be done right. Either way I want to feel a little more confident trying to power through a 20-knot head wind, on a 10-mile passage!