Engine coupler failure

[Scottyd2002]

Have a 2005 Mercruiser 4.3 in a 23’ sylavan and have replaced the engine coupler twice in 3 years.
Have checked alignment and everything I can think of so far
could running at too low RPM due to incorrect prop size cause this?
the engine can only turn about 2200 RPM at full throttle???
should be up around 4000 ?
it has a 15x19 prop.

 

[Bondo]

the engine can only turn about 2200 RPM at full throttle???
should be up around 4000 ?

Ayuh,..... Welcome Aboard,..... You've got some Serious issues goin' on,...... it should be close to 5,000 rpms at Wot,.....

Sounds like it's the Wrong drive for starters,.....

Trollin' is in fact tough on couplers, especially if not well greased,.....

 

[Bt Doctur]

I agree with Bondo sounds like a 1.50 instead of a 1.84

 

[alldodge]

could running at too low RPM due to incorrect prop size cause this?

Agree, grease is needed, but if your alignment is spot on, then check your front motor mounts. They may be loose of stringer is soft and motor is twisting.

When checking alignment, are you turning the motor 90 degrees and rechecking?

 

[Scott Danforth]

I would seriously be looking at your tachometer. If you are lugging the motor truly at 2200 RPM you have major driveline issues. You could just simply be off on your tach in addition to alignment issues

 

[Bt Doctur]

when replacing couplers you should also replace the rear mounts, they will throw of the alignment too if they start flexing