Yeah, you're right. The 4-108 is nowhere near a 50hp engine
as some claim. I put it closer to 30hp.
The super duper mechanic
who finally put me straight (a friend I flew down to St. Thomas after dealing with local mechanics, including ex-pats, for years) told me that if the heat exchanger
were working properly and if the engine
were not over-propped, it should be possible to to push that engine wide open for a long time without overheating
After doing his magic -- and finding several things wrong -- he made me power at full speed from Nanny Cay in the BVI up the Drake Channel to Cooper
Island. Sure enough, no overheating
But, that was with a NEW heat exchanger
, and everthing tweaked up right.
After I fitted the larger heat exchanger a couple of years later (having again experienced overheating), I've had no more problems.
Conclusion: that heat exchanger on the 4-108 is too small, especially if you're sailing in warm water
temps in the tropics.
, I can power at 2500-2600 indefinitely, but use a lot of fuel
. I find that 2300-2400 suits me better. My boat has a 17" 3-blade MaxProp and weighs about 27,000 lbs.