I have a 1985 15sk that I bought a few years ago and had it worked on because it was stuck in the forward gear. When I got it back I took it to the lake and ran it to see how well it would perform. It ran fine for a few minutes but then I had a loss in power/speed at full throttle. It runs great at half throttle but immediately has the loss at full throttle. I spoke to the shop that worked on it and they wanted me to bring it back to them (after an argument about a seal kit that may or may not have been installed) but I do not like the way I was treated and they were VERY expensive. I am trying to run it on a 1448 flat bottom jon boat and my father seems to think that the problem is cavitation, but I know nothing about this. The prop is a little worn but nothing serious and I have checked the splines inside the prop, and on the drive shaft. Ive also checked all the bearings and there appears to be no problem with any of them. Does anyone have any insight as to what the problem may be?