CMC Power tilt and trim mounting height calculation?

[ShoestringMariner]

Hey folks, I've got a CMC PTT that I bought used. I'm mounting it on my aluminum boat (1975 Starcraft SS160).
The manual I found online states that the cavitation plate needs to be mounted 1-3" higher than the bottom of the boat due to the 6" setback of the motor from the hull. But also warns not to set it too high that I lose water pressure at top end

So, how can I be sure I have the optimum height set up? I heard that for every inch of setback, it should be 1/2" of rise. By this rule, it sounds as if the motor should sit 3" higher than its original position which is on the top end of what the manual recommended.

I don't want to have to re-drill holes in my newly rebuilt transom if I get it wrong. It does not have a jackplate. Do you guys think I should air on the side of caution and go only 2 to 2-1/2" higher or am I worrying about this needlessly?

 

[GA_Boater]

I would mount the CMC at the same height the motor was before the transom redo. Pretty much flush with the top of the transom.

After the CMC is installed you raise or lower the the motor on the CMC unit to optimize the motor height for the setback. No need to re-drill the transom.

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