Hi friend's, I 've an 35'Bertram(1975) I did my engines 6bta cummins 330hp 5.9lts. After start on sea, my boat is doing 12-14knots and black smoke. Somebody else have this engine with zf transmission?? I need know about my correct propeller's size.Turbos and intercooler are ok. Diesel injection was in revision. I'm thinking in propeller's problem's.