Rattle near stern gland?

[timj]

Hi

On our last trip out we noticed a rattle audible inside the aft lazarette which seems to come from the prop shaft. We hear it only at about 1500 rpm. Below that there is no noise. And as we throttle up above 1500 rpm it disappears also.

We motored home at 1900 rpm and all seemed well. I dived and checked the shaft zinc and the prop shaft itself appeared firm with no slop in the cutless bearing.

The bearing was my first guess? Then I thought it might be a loose zinc but they seem OK.

The vessel is a 10 tonne semi displacement NZ built trawler style with a CAT 3208 NA driving a 2 inch shaft.

Any thoughts appreciated!

 

[RickB]

Bump the rudder.

 

[Moonstruck]

Sounds like a cutless bearing. If not could be the rudder. My bet is cutless bearing. If you can get under the boat, see if you can move the shaft or rudder even a little. That would be enough to do it.

 

[Nomad Willy]

I had a rattle in my stern for a long time and thought it was the rudder brng at the end of the shoe but recently I discovered it was the mounting plate for the slave cylinder that drives the rudder horn. Loose bolts there were to blame.

 

[Brooksie]

Where rudder sits in skegbar, if fitted.
Prop loose on shaft.
Rudder tiller arm or quadrant as fitted.
Eng. to Trans. drive plate, being transmitted to lazarette through shaft.
Your cutless bearing would have to be worn through to rattle.

 

[Marin]

Your cutless bearing would have to be worn through to rattle.

Not necessarily. We had a driveline rattle on the port side and it turned out to be a cutless bearing that had simply loosened up a bit and was starting to "walk" out of its housing on the Vee strut.

The other suggestions--- rudder, part of the steering gear, etc.--- seem logical things to check for sure.

 

[timj]

Thanks for suggestions. I found that our hydraulic steering lines were rubbing on a newly installed bilge hose. Hopefully this is the issue. Will checkout today on sea trial. Thanks again