After doing a motor upgrade to a Suzuki 70hp 4 stroke a few years ago I decided to retire my 1987 Alumacraft Classic side consul for a new 05 Alumacraft Magnum 165 CS. At the dealership they installed my engine at the 2nd to lowest setting and the boat porpoised significantly even at the lowest trim settings at increased speeds and had significant spray from the front of the engine. I had the dealership increase the engine height one hole and performance improved but still porpoising at anything above the lowest setting on the trim gauge. I tried raising the engine to the highest setting and still I have to have the engine trimmed way down. On the older flatter bottomed boat I could trim the engine way up with my 17 pitch cupped edge prop and never experienced porpoising as the prop would break the surface before that possibility could occur. The new boat is at least a few hundred lbs more and a v-hull but I find it strange I have so little ability to trim up when running before the boat begins to bounce. I have two forward mounted trolling motor batteries and the starting battery in the rear. I'm not sure if this is normal for this style of boat but I guess I was expecting a bit more ability to trim up. Overall the boat handles great but rpm seems to be down about 300rpm to 5500 and top speed decreased a few mph from the old boat with the same engine.
I'd appreciate any comments or advice on this issue of porpoising. Maybe smart tabs would help out but though maybe others might have a similar boat and motor combination. The boat is rated up to 90hp and is almost identical in weight and hull dimensions to the new Alumacraft Classic/pre 05 Navigator boats.
I'd appreciate any comments or advice on this issue of porpoising. Maybe smart tabs would help out but though maybe others might have a similar boat and motor combination. The boat is rated up to 90hp and is almost identical in weight and hull dimensions to the new Alumacraft Classic/pre 05 Navigator boats.
