[PCW] FP horsepower increase

[Pat Reischmann]

I suspect the FP hull designs are very similar to the Manta, CS, Maine cat,
and other "displanning" hull forms as Pete Brady would call them. These hull
forms are very efficient in the displacement mode and the mid range 15-18
knots semi-displacement mode. Adding more horsepower after a point doesn't
seem to add much more speed nor efficiency. I think some people don't
understand the distinction of difference between these hull designs and full
planning hull forms (symmetrical and asymmetrical).
All out planning hull forms actually become more efficient at the higher
speeds than the displacement type hulls, but don't enjoy the low speed
efficiency, sea-kindliness, and fuel economy in the mid range of the
displacement type hull forms. The Manta is a good example. With a pair of D-3
160 hp engines top end is 19 knots, with the D-4 225 hp 21 knots, with the 250
hp 23 knots.
Based on overall efficiency, noise, etc we found the 225 hp to be well suited.
At 75% throttle the 160 would cruise at 15 knots,
the 225 at 17 knots and the 250 19 knots. I think FP is probably giving good
advice about hp increases.