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Old 02-26-2008
Northeaster Northeaster is offline
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Rebuild 2GM vs repower with 2YM15 or 2YM20

Hi Folks,

My mechanic brother is about to check out my 25 year-old (raw water cooled) Yanmar 2GM. The engine was smoking a bit at high RPMs / High load, but otherwise worked well. I did have an issue where the raw water flow stopped a couple of times, but when I pulled off the water hose on the exhaust elbow, there was a poof of dry air, then the water flow came back right a way, and worked fine after that. May be an intermittent failing water pump??

Anyway, he will do a compression test, possibly an oil analysis, and check the head (valves, valve seats, etc.) If all check out OK, He will replace gaskets, and I may still spend about $500-1000 for new engine mounts, and a rebuild (or gasket kit) on a 25 year old engine - that has been raw water cooled, in salt water, for 25 years.

I don't have extra cash!! But, I can get a new 2YM15 for $5800 + tax. or a new 3YM20 for $6900.

Any advice would be appreciated! If my engine does not test well (compression, oil analysis, or look at water jacket, etc), do you think it would be wise to replace with an engine of approx same HP (2 YM15), or, as they say most boats are underpowered, and we have strong tides in the area (35 ft tides, on the Bay of Fundy) - Should I consider the 21 HP (3YM20).
I assume that I would have to look at re-propping, or at least re-pitching, if I went with more power. I have an old fixed 3 blade prop, on my current 13HP (2GM)
The boat is a 1978 Seafarer 30 (book disp 8600lbs, crane said it weighed 10,000, with gear onboard)
- A new 3YM20 is only 38lbs heavier than a new 2YM15!
- I do plan on keeping the boat for the next few years, at least.
- My water heater would be much more efficient with a fresh water cooled engine
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