Cavitation plate v. bottom of boat distance

[skanders01]

Is there a minimum distance recommendation between the bottom of my ’62 Alumacraft FD6 and the cavitation plate for my CD-11’s? Don’t have a competition boat here, so I can push the minimum recommendations a bit if need be….just need a starting point. I need to raise the motors to get a little extra clearance between the motors and the sides of the raised transom corners for my multiple motor mount setup by raising the motors.

Thanks in advance for any advice.

Kyle Anderson
Trempeleau, WI
skanders@triwest.net
920-764-0501

[chinewalker]

Every motor and boat combo is different. If you’re looking for a little less draft, start with the motor flat on the transom. Run the motor and note whether it ventilates or does anything untoward while operating, particularly if the motor is turned sharply at speed.

Cut up a couple of cheap yard sticks into 8-10 inch sections. Place one under the clamp bracket and go run the motor. Again, note any ventilation issues or anything else that isn’t supposed to happen. Place another stick under the motor and repeat. Continue until the propeller ventilates.

Keep in mind that you must maintain a firm clamp grip on the transom for safety. If the clamps run out of transom before the motor runs out of water or sucks air, consider adding a bracket to safely facilitate higher mounting position.
Also, keep an eye on water output as some motors may not pump water properly when the motor is raised on the transom.

[garry-in-michigan]

It depends on the boat construction and motors purpose. This diagram is basic to the late 1930s and works with great reliability. This would be maximum depth with a good load. More free running boats or light loads will give more speed with less motor in the water. For these boat and motor combinations, follow the directions of the previous post. . . 😉

[skanders01]

Thanks for the diagram, Garry. Sound like ultimately the proof is in the motoring around.

Kyle Anderson
Trempeleau, WI
skanders@triwest.net
920-764-0501

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