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Transom Height

Posted: Tue Dec 14, 2010 11:02 am
by JALL
The Cruisers Inc I'm working on has a built up transom. The height is 19.5 in. which is about 3.5 more than original. I have two 1957 Johnson 35HP motors to put on it. These motors are not the long shaft models. The question is should I leave the transom at 19.5" or get it back to the original 16"? I almost think the motors would work with the 19.5" Thanks for any help!

Posted: Tue Dec 14, 2010 12:10 pm
by Torchie
I am running twin 57 johnsons on my Thompson.
My transom is about 19 1/2" where the motor mounts. My 35's are the long shaft which leaves me about 15" of lower unit hanging below the hull. Plus the added depth of the hull dispalcement in the water.
Is there any water marks (Pond scum) on your lower unit. if so how far above the water intake are they. That would help tell you how deep they would have to go or at least have been. Hope this helps.
Karl.

Posted: Tue Dec 14, 2010 12:32 pm
by Phill Blank
JALL,

If you are going to be running older stadard leg length lower unit outboards, you will need to lower the transom height. The anti-cavitation plate just above the prop, should be at or slightly lower then the bottom of the hull. These older motors with standard leg length are designed to run on a 15" transom height not the taller height for the long leg motors.

Cut it down or find NOS long legs for the motors.

Good Luck,

Phill

Posted: Wed Dec 15, 2010 6:37 pm
by JoeCB
Remember that transom height is measured along a vertical line, not along the inclined face of the transom.

Joe B