Great analysis JohnC!
As far as props are concerned, I was told by the folks at PowerTech that a 4B prop will always develop more stern lift than a 3B prop simply because of the extra blade. However the blade design and shape can also make a lot of difference. I've read that props with more rake to the blades are supposed to create bow lift, while props with less rake generate stern lift, but I'm sure there is more to it than that. I have a 14 1/8 x 21P 4B Michigan Apollo that is supposed to be a bow lifting prop that I can trim out to about 75% before it starts to porpoise, but my stern lifting 15 x 15 4B PowerTech prop will start to porpoise over about 50% trim, so there are probably a number of variables involved. Ed, it might be worth a call to Ken at Prop Gods to see what he would recommend for Pitch/diameter and style of prop to minimize the porpoising problem.
I have checked the prop shaft angle vs engine trim and it appears to be parallel to the keel at 50% trim, so I don't think there is an efficiency penalty for running at that trim setting.
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