Re: Prop for Suzuki DT140 on a 20' MA?
You want to be able to turn the maximum end of the maximum recommended rpms with the boat at maximum loading.
That's "Max of Max at Max"
A quick look shows your DT140 has a recommended maximum RPM operating range of 5250-5750 rpms. So you want to be able to turn 5750 rpms even with the boat at maximum loading.
Mount the motor so your cavitation plate is about 1.5 inches above the keel line of the hull with the motor at neutral trim (parallel to the hull bottom). I'm guessing a good starting point for a Suzuki prop for you would be a 13 1/4"Dx18"P SS. Assuming 10% slip, you should get around 40 mph at WOT 5750 rpms.
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Common Sense is learning from your mistakes. Wisdom is learning from the other guy's mistakes.
Fr. Frank says:
Jesus liked fishing, too. He even walked on water to get to the boat!
Currently without a SeaCraft 
(2) Pompano 12' fishing kayaks
'73 Cobia 18' prototype "Casting Skiff", 70hp Mercury
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