bigdogeh
Well-Known Member
That engine (if it's a mercruiser D4.2L) should be able to reach 3,400 to 3,600 rpm at WOT. If not, now that the bottoms been cleaned it's probably overloaded and needs to lose some weight. Or as others have mentioned go down in prop pitch and/or a 4 blade prop would prob help for more bite. I'd also remove the air filter and check the turbo to make sure it spins freely, no broken blades, tight housing clearance (no housing corrosion) etc... replacing fuel filters if they haven't been done in awhile wouldn't hurt also...
Those engines usually sip fuel and are very efficient, especially at the lower rpm's. And usually virtually smokeless which is nice. The odd one has been known to break (snap) the crankshaft at the balancer so check the balancer every once in awhile and make sure no rubber is protruding. (the thin rubber strip that joins the heavy rings...) They usually snap at high rpm's if it's going to snap. I'd want to make sure my marine insurance policy covered engine replacement in that respect if running that engine often at close to WOT. Just saying... My opinion is that the crankshaft is designed a bit light in that area. Compared to a Cummins, the differences are night and day.
Those engines usually sip fuel and are very efficient, especially at the lower rpm's. And usually virtually smokeless which is nice. The odd one has been known to break (snap) the crankshaft at the balancer so check the balancer every once in awhile and make sure no rubber is protruding. (the thin rubber strip that joins the heavy rings...) They usually snap at high rpm's if it's going to snap. I'd want to make sure my marine insurance policy covered engine replacement in that respect if running that engine often at close to WOT. Just saying... My opinion is that the crankshaft is designed a bit light in that area. Compared to a Cummins, the differences are night and day.