James, I have the Same boat!. '76 30 TF repowered in 2011. I viewed your Prop Size PDFs and really appreciate the data. can you confirm that this was done with 18x20 3 blade props. if so ... this is the answer i've been looking for. I am running 17 x 17 3 blade and i have a spare set of 4 blade. but feel the boat just doesn't go as fast as it could. several friends feel the same way as when we run with a little gear, gas and water we only get to 16 knots at 3100 rpm. i really feel we should be at 16 at 26-2800. as it appears you have reported.