Further to my previous posts, I picked up the boat again in September and low and behold no prop whine. I donned goggles to find that the prop was covered in barnacles and bits of weed, (thats what 4 months of Med does).

This would then suggest that it was the props cavitation setting up a horrible harmonic. Good to know that it was not the gearbox. Probably will purchase a folding prop when the boat comes off of charter. And by the way the performance of the prop led to a marked decrease in boat speed. Will let you know if the whine returns in May 2012 when the boat returns to the water.