KAM
Well-Known Member
I thought I would share this in case it helps anyone else. Several years ago I re engined and installed a skeg mounted prop shaft. (Not a P bracket) Looking around the internet for design guidance I copied what I saw in pictures and seemed to be common practice on some well known production boats and left the trailing edge of the skeg just forward of the prop blunt. It was easier to do structurally at the time and I thought it would be stronger. Everything worked well but I had always been disappointed with the cruising revs performance and prop noise and vibration from the 2 bladed folding prop. I put this down to lack of hull clearance as I could only get 50 mm with the difficult geometry of the new engine installation and the cheap folding prop. I had been thinking of changing the prop but this winter I decided to fair the trailing edge to a relatively sharp edge. It cost about £10 in materials and about 5 hours labour. The improvement was staggering. Cruising revs at 5 kts dropped from 2400 to well below 2000. Most of the vibration disappeared and the noise was much reduced. Probably a bit obvious really but there seem to be a lot of boats out there with poor skeg design. I'll maybe try a bit of pre swirl next year.