@spencerd wrote:

    Any ideas on a high pitch whine from the saildrive from about 1200 – 1800rpm. I have been told that it comes from the prop cavitating!! and a cure is to ‘sharpen’ the leading edge of the prop. The boat is a B44 and is a dream apart from the whine.

    It is indeed due to cavitation. I did an experiment, being towed close behind the boat watching the propeller – not for the faint hearted! As the revs got to the critical point, a mass of bubbles appeared like a vortex behind the propeller; it actually looked quite stunning. All was cured by a new propeller, after the old one got damaged.

    I had tried altering the leading edge, but I was told by Volvo Penta to blunt it, not sharpen! I think it would be best to get definitive profile information before proceeding.