R31 Drive Rumble Trouble Shooting

[HopTug]

We were unfortunate enough to strike a log or rock back in July, requiring a prop repair and a cutless bearing replacement. I still hear a "rumble" coming from aft of the engine that I'm pretty sure wasn't there before. It's inaudible at 1400 RPM, but comes in by 1500 RPM and is audible until passing about 1900 RPM where it seems to quiet down.

Again, cutless bearing is new, engine was aligned, and prop shaft has been checked to be true. Rumble doesn't occur when I rev the engine to 1500 without engaging the transmission. Any ideas? Would damage to the packing create a sound like this?

Thanks!

 

[bob daily]

When you say rumble not sure what you are trying to describe, sometimes when a high pitch noise or a whining at certain RPM' s is caused by cavitation also called (prop-sing). Since this started after the work on the prop that is where I would look. Bob

 

[HopTug]

Thanks Bob, definitely not prop sing as I’ve tried 2 different props. It’s more of a low pitched rumble or grinding sound. I thought it would go away with the cutless bearing change, but alas, no.

 

[GaylesFaerie]

Recheck/tighten the motor mounts?

 

[Red Raven]

With engine off try rotating the shaft by hand and listen and feel for any grinding or noise. If the shaft is contacting the stuffing box at any time that could cause the noise you describe. You can also check for continuity between the stuffing box and shaft with a multimeter while turning the shaft. If you get continuity at any point then that could be the cause. The shaft should never touch the stuffing box. If it does you will need to readjust the shaft alignment.

Curt

 

[piglet 2013]

If the engine was aligned out of the water sitting on stands it might need to be re-aligned as the boat hull might have been tweaked on the stands and then settled out when it was put back in the water.