I have looked though as many as the threads on this as possible and can not find anything I have not already tried. Ok here is the situation. I have twin Mercruiser 1985 350's inboards in a Wellcraft. Both rebuilt at the same time, Recently switched from 3 inch exhaust to 4 inch exhaust. Starboard engine does not come up to RPM. When throttles advanced, goes to about 2500 with out issue then as the other engine take the load off will advance to 3200. Sometimes will stay there, Sometimes will just pause there for a few mins, then will go on up to about 3600, Port engine is in the target range of 4400 RPM. OK now for the things that I have tried:
Rebuilt carb. no effect
Swaped carb, to other engine, No effect
Swaped coil, no effect
Replaced Plugs and wires, no effect
Pulled props and checked pitch, was good,
Cutlass bearing and gear box check out good, (will turn freely by hand)
Replaced lifters, on starboard engine No effect
Replaced complete Disturbutor assembly, No effect.
Swapped electronic ignition, No effect
changed fuel filter Nope
Ran engine straight from 6 gallon fuel tank, elimating all fuel lines before the fuel filter, Nope.
Convinced it is not a tach problem, you can hear that the engine is not running up. And at a lower RPM, you can hear them when they synk...
Engine ran good after rebuild, and after exhaust upgrade, the problem has slowly developed, or it has taken me a long time to notice it. I normally cruise at 3300, to 3400 RPM, Never run at WOT for long
Any Help our suggestions would be greatly apprciated!
Rebuilt carb. no effect
Swaped carb, to other engine, No effect
Swaped coil, no effect
Replaced Plugs and wires, no effect
Pulled props and checked pitch, was good,
Cutlass bearing and gear box check out good, (will turn freely by hand)
Replaced lifters, on starboard engine No effect
Replaced complete Disturbutor assembly, No effect.
Swapped electronic ignition, No effect
changed fuel filter Nope
Ran engine straight from 6 gallon fuel tank, elimating all fuel lines before the fuel filter, Nope.
Convinced it is not a tach problem, you can hear that the engine is not running up. And at a lower RPM, you can hear them when they synk...
Engine ran good after rebuild, and after exhaust upgrade, the problem has slowly developed, or it has taken me a long time to notice it. I normally cruise at 3300, to 3400 RPM, Never run at WOT for long
Any Help our suggestions would be greatly apprciated!