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Author Topic:   Why Raise Engine on Transom

AKwalor posted 05-31-2004 12:22 AM ET (US)
I've been reading about raising your engine on your transom. I have never heard of this, and I have always been told you mount your engine where the [anti-ventilation] plate is flush with bottom of your hull.
What exaclty happens when you raise your engine? How do you know if you should do it or not?
jimh posted 05-31-2004 08:02 AM ET (US)
The relationship of the engine to the transom is incidental. The reason the engine is raised is to reduce the amount of wetted surface of the lower unit in the water. This reduces the drag. Less drag means more speed.
As an additional benefit, the lever-arm of the thrust (where it acts against the hull's center of pitching resistance) is shortened, and in some cases this may produce an improvement by decreasing a tendency for the hull to oscillate in a pitching motion (often called "porpoising").

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Author	Topic: Why Raise Engine on Transom
AKwalor	posted 05-31-2004 12:22 AM ET (US) I've been reading about raising your engine on your transom. I have never heard of this, and I have always been told you mount your engine where the [anti-ventilation] plate is flush with bottom of your hull. What exaclty happens when you raise your engine? How do you know if you should do it or not?
jimh	posted 05-31-2004 08:02 AM ET (US) The relationship of the engine to the transom is incidental. The reason the engine is raised is to reduce the amount of wetted surface of the lower unit in the water. This reduces the drag. Less drag means more speed. As an additional benefit, the lever-arm of the thrust (where it acts against the hull's center of pitching resistance) is shortened, and in some cases this may produce an improvement by decreasing a tendency for the hull to oscillate in a pitching motion (often called "porpoising").