Re: Prop Question
Hello Ken,<br />I'm not sure if I can give you the best advice but I'll give you what I know. I have a 21' GradyWhite 1976 CC. I repowered the boat this year and in doing so had to build the transom up to accept the new engine. Previously I had a 150hp Evenrude with a 20" shaft. Now I have a 150hp Johnson with a 25" shaft. To get the transom height that I needed for this new engine I had an alluminum plate made, that would slip over the existing transom, but was also designed to give me the added height that I needed. While exploring ways to build up my transom I had to take into account the structural integrity of the boat itself, the weight of the engine, and the force that would be applied to the transom by the engine when operating and trailering. I'm not an engineer but, with a lot of help from the local marina's, and library, I was able to design this plate and keep all of the standards I had to follow. The plate is made from 1/4" thick alluminum plate. Where the plate rises above the old transom I had a cross member welded in every 4" (this measurement was derived by the amount of space I had to span, and the properties of alluminum itself, and then doulbled to satisfy my insecurity) Meaning I only had to space the cross members every 8". I then lowered the plate over the transom until it sat on the cross members, bolted the plate to the transom, and then drilled the holes for the new engine. The lower two holes in the engine went through the transom, as well as the bolts the held the plate on giving me 6 bolts in the transom and plate to hold it securly to the boat. When finished the plate cost me $136.00. I'm sure you would be able to do something similar with OAK as long as you took all aspects of water, transom integrity, and engine force into account. As for the prop, go to the local marina's and the library. There are formula's written, that are available to you, to match you boat & engine to your propeller needs.
<br /><br /> Thanks