reviving old seacraft (propeller question)

[Fr. Frank]

Dixon, have you measured the angle of thrust on your motor at operating trim angle? If you cannot trim at all without ventilating your prop, that means you're probably at a negative trim angle (thrust angle aims slightly downward), and if so, you're running too high out of the water. You need a positive thrust angle of at least 4-5 degrees, or you're literally driving the bow down into the water, creating a lot more drag. You want to get the stern up, then you want to lift the bow for best speed. If you run with your motor trimmed all the way down, put a carpenter's protractor on it and measure the angle to the cavitation plate. If you don't have access to a big protractor, just stick a long level or good straightedge along the keel line of the boat. If the cavitation plate is exactly parallel with the keel line, or the front of the cavitation plate is higher than the rear, you need to adjust your mounting height upward. You need about 10* of negative trim (trim "in") to get on plane, then you should run at about 4*-10* of positive trim (trim "out" or "up") at full throttle.