Hi Folks.
Last year we had a refurbed Perkins D3 with a 2:1 PRM (also refurbished) fitted. At the same time the prop shaft was changed and the packing renewed. We only picked it up at the end of last season and it had about 12 hours of running back to base - and then we took her out again this weekend. On Friday we had this loud harmonic sound that seemed to start when the engine was put in gear to pull away out of a lock; it did this twice. It didn't seem to go when additional revs were put on - what seemed to shift it was a sharp rev in reverse. I checked the weedhatch and there was only some light weed around the shaft. I could turn the prop in neutral by hand through the weedhatch.
I did notice on our return that the noise did seem to build up slowly - but a quick rev in reverse seemed to clear it.
Some possibly useful (most likely useless!) additional info
The prop was not changed at the time the engine was changed, to my knowledge, it has not been 'clonked' against anything hard - but it may not be the ultimate size for the boat now.
The stern tube does not leak a drop in forward, but I note does drip in reverse
I'm not sure if the shaft is getting warm as there does seem to be some grey grease on the shaft between the stuffing box and the centrafex coupling
The engine is on solid mounts.
There is a 'clonk' when engaging gears - I have had this before on a PRM, but its not a comfortable sound!
It does seem like a prop singing noise - but why would it clear itself when reversed, unless it is a slow build up of crap on the blades?
Any ideas very welcome
Thanks