Re: 3cyl 65-70-75 OMC Rebuild

[DAN ANDERSON]

Your ’89 model is a 56 cu in powerhead. The (60,65,75) motors you are referring to are 49 cu in powerheads. Different engines. When your engine was rebuilt was it modified? A service bulletin was written with steps to improve durability after rebuilds to this motor? Starting in 1986 when this motor became 56 cu in it picked up a larger exhaust port with a bridge. The bridge could give problems with ring breakage in some circumstances. I can try to get the number or a copy. The ’86 60hp engine did stay 49cu in until ’89. As far as modifications I can’t think of anything I would do except make sure it is running as well as it can. WOT should be as close to 6000 RPM trimmed out as you can get. That will give you a decent hole shot and keep the engine cool at WOT. Your machine shop needs to know what mods to do to the exhaust port. Hope that helps!

Dan in TN