410: Cavitation problem

[Pavo Real]

I have a Lagoon 410. The starboard engine has a SD 50 saildrive. When I have a following sea above 4 feet quartering from starboard aft I get a cavitation like vibration from that drive. Happens as I ride up the wave front. Only happens under those circumstances. All quiet and no vibration in any other conditions. I've visually inspected the prop and there does not appear to be any obvious damage or warping. Still, is there anything that could cause this except a bent prop?

[careka]

do you lock the gear in rev as you sail, or is it in free ? so it can turn around ?
is it a fixe or folding on ?

[Pavo Real]

I have 3 bladed fixed props. The cavitation occurs when the engine in operating and at all RPM's.

[careka]

OK, fixs prop 3 blade, and full speed ? you must not do that for a long time, let say 300-400 below what you get at full speed, that can be maks cruse speed.
and your prop blades can have a small damage that will make vibrasions.