Possible Lower Unit Problem

[bayhawk14]

Took the boat out this weekend & noticed a vibration when in low rpms' going forward. I just changed the lower unit oil & found the normal metal fuzz along with very small & thin pieces of metal (fall apart in your fingers). In addition, I recently removed the lower unit to change the water pump. Could this be a shifting problem or worse? When running on the trailer in gear at low RPMs' it knocks & bumps. Reverse seems to be ok.. I removed the cowling & in forward gear looks like the pin is moving all the way forward. Thanks!

 

[rodbolt]

Re: Possible Lower Unit Problem

what model number are we dealing with?

 

[bayhawk14]

Re: Possible Lower Unit Problem

1998 Yamaha C115

 

[rodbolt]

Re: Possible Lower Unit Problem

usually the only time I have a V4 that chatters on the flusher its either a loose prop or an engine miss.
the 3.1 is another story.

 

[rodbolt]

Re: Possible Lower Unit Problem

theV76 3.1L runs on 5 cyl at idle and with a big stainless wheel the clutch rattles as the shaft unloads and loads when the dead cyl comes up.
you can check the torque on the prop nut, most are about 50ft pounds.

 

[rodbolt]

Re: Possible Lower Unit Problem

describe for me the EXACT procedure you used to reinstall the lock collar and the three metal plates on the impeller.