rumble

[dsw]

any one got any idea why i have got a rumble at 1400 rpm as if i was driving a car 5mph in 5th gear ? its ok under and over that rpm and i have two r&d couplings and my shaft is fixed to the hull (steel) with a pillow block and stuffing box and 20 inches to the gearbox flange(prm750d)

 

[srp]

Broken engine mounts (sometimes they look ok when the engines stopped but the rubbers parted company from the mounting plate). Or possibly a knackered cutless bearing - is the boat in the water? Or the final drive shaft bearing at the back of the gearbox has given up.

 

[Richard10002]

or could it be just a new resonance at those revs?

 

[damo]

I'd look at the cutless bearing first - similar symptoms on mine earlier this summer, and that was the reason.