Minnesota boater
Cadet
- Joined
- Jul 13, 2012
- Messages
- 11
Replaced my 3.0 when I put a rod through the side Labor Day weekend last year (glad it wasn't Memorial Day) bought a 3.0L GM marine engine from Michigan Motorz. Did the break in period of 10 hours, have run engine another 10+ hours.
Will not develop rpms above 3700-3800, will not get out of the hole unless I put a couple people in the bow.
Prop is a 3 blade 14"dia 19P, well within the specs for this motor to get to 4500 rpm. Using the same boat, same outdrive, same carb, same fuel pump, etc from the old engine. Compression is 160-160-175-175 front to back. Have disassembled both fuel filters (clean). I put in a clear in-line filter last year because I've had bad luck with the standard filter in the pump (ceramic one clogged, cardboard replacement buckled). New cap and rotor came with engine, plugs and wires are new. Replaced plugs, no change. Timing is in spec. I can manually rev up the engine to 3800 rpm if I disengage the throttle linkage and work it by hand (yes someone else is behind the wheel
).
Could I be out of alignment bad enough with the outdrive? I spoke with someone at a marine shop who said that as long as I had no trouble getting the outdrive into the spline it should be fine.
Other symptoms: stumbling at idle and hard starting (needs some throttle to catch and even then a lot of cranking to get it done). For this reason I took the carb apart and cleaned all the components. Noticed the rear venturi was dripping much faster than the other and swapped venturis but that didn't change anything.
I'm at my wits end. I can easily get 4000+ on muffs no hesitation. Seems like a fuel issue but why would everything change so radically?
Your advice is greatly appreciated. I'm no master mechanic but I don't mind getting my hands dirty so I'll do whatever I get told to do...lol
Will not develop rpms above 3700-3800, will not get out of the hole unless I put a couple people in the bow.
Prop is a 3 blade 14"dia 19P, well within the specs for this motor to get to 4500 rpm. Using the same boat, same outdrive, same carb, same fuel pump, etc from the old engine. Compression is 160-160-175-175 front to back. Have disassembled both fuel filters (clean). I put in a clear in-line filter last year because I've had bad luck with the standard filter in the pump (ceramic one clogged, cardboard replacement buckled). New cap and rotor came with engine, plugs and wires are new. Replaced plugs, no change. Timing is in spec. I can manually rev up the engine to 3800 rpm if I disengage the throttle linkage and work it by hand (yes someone else is behind the wheel
). Could I be out of alignment bad enough with the outdrive? I spoke with someone at a marine shop who said that as long as I had no trouble getting the outdrive into the spline it should be fine.
Other symptoms: stumbling at idle and hard starting (needs some throttle to catch and even then a lot of cranking to get it done). For this reason I took the carb apart and cleaned all the components. Noticed the rear venturi was dripping much faster than the other and swapped venturis but that didn't change anything.
I'm at my wits end. I can easily get 4000+ on muffs no hesitation. Seems like a fuel issue but why would everything change so radically?
Your advice is greatly appreciated. I'm no master mechanic but I don't mind getting my hands dirty so I'll do whatever I get told to do...lol
