I could use some advice on the proper transom height for my '79 35hp short shaft(I think?). the measurement from the top of the mount openning to the AV plate is 17.5" and my transom is cut down to 18". the AV plate is 1/2" above the bottom of my 1648 v jon boat. my problem is at a hard take off and at WOT the prop starts to slip and the rpms go up and the boat speed goes down. the prop is in good shape and it is a 10x15. Can anybody please help on what to do next.