Intermittent rattling/grinding on FWD idle after 3600 RPM load after gimble/U-Joint replacement

replaced gimble, ujoint, shift cable bellows and annual service. afterwards, unable to plane @ 3600 RPM, though engine sounds good and is not over-revving. After 15 min @ 3600 RPM load and unable to plane, upon subsequent FWD idling (1000-1500 RPM), I heard intermittent and subtle rattling/grinding sounds and felt vibrations which seemed to be coming from drive or possibly engine compartment (had too many peeps onboard to get a visual). Could it be flappers, spun prop hub or flywheel damper? Given the fact it was just serviced, could it be something the mechanic forgot to reseal or what not? Please help as I am baffled. Thanks Jeff - 1988 mercruiser 330 HP Apha One (IOU)

Mabe you should take it back to who ever serived it.isthe eng is runnig right mabe plug wire fell off? Pull the prop take to a prop shop and ck it if its good i would pull the drive take a look at the u joints mabe one is starting to come apart?clips might have fell out no noise should be there. Then it could be damper? If damper or prop is bad eng revs but no plane.good luck

over heated and the flappers are rattling

kghost said:

over heated and the flappers are rattling

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Engine temp was*normal throughout; no evidence of engine overheating.* Actually, the rattling sound is*accompanied*by a*slight vibration/surging*effect that I experience while*FWD idling*(1100-1500 RPM) immediately following*load (i.e. 3600 RPM FWD for*15 minutes).* Could this surging/vibration with concurrent rattling sound be a manifestation*of a slipping prop hub?* Even*at such*low RPM's (i.e. 1100-1500 RPM)?**My prop is 6+ years old and*it is*a merc original*equipment*prop (not aftermarket).* I was told the hub is the better hub (i.e. not rubber).

Regardless, I*notified my*mechanic who*just replaced gimble & u-joint, but*has not returned my calls perhaps*due to the holiday.**Still, if only my prop is bad,*I can easily replace that*in the slip Vs paying for yet another haulout - I have no trailer.* T

he weird thing*is the rattling/surging/vibration*went away after about 10 minutes (post load) of FWD idling in the harbor...could this still be a*slipping prop hub?**My worry is that my mechanic will most likely NOT*be able to reproduce this problem*in the harbor (since problem*went away after a several*minutes of post load idling).**As such, he would most*likely have to sea test the boat*for a definitive answer...$$$...* As such, and as an alternative, I'm hoping*this forum can produce*an opinion as to whether or not what*I*am describing and experiencing sounds*potentially like a spun or slipping hub.*

My past experience with*spun hubs was very obvious at least with*after market props.* They*just revved like crazy above 2500 RPM's and I had to back down*to about 1500 RPM for it to catch and make immediate*return to harbor - that's it - simple.* But this problem is more difficult for me to diagnose.* Thanks for any help whatsoever!*