I once rigged for her owner a 20' CC, installing a 20" Merc 225 on a mechanical jackplate, with a low water pickup & nosecone. Cruised in the intercoastal at about 3800 rpm at 45 mph. Top speed was 62 mph at 6000 rpm running a 32" overhub chopper style prop.
The real story here? It was owned by 24 yr. old female attorney from Palm Beach who was given the boat by her Dad as a present for passing the bar exam.
It was fun to watch her flying down the waterway at 60 mph in a SeaCraft with a huge rooster tail behind her.
Do you need that much power? No, of course not. Sure is fun, though.
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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