Propeller size

[rich10]

Updated information 8/3/16:

Hello, I have a 1970 20' Sea craft c.c.. It has a aluminum t-top, electronics box, original console with a 3/8" windshield extended to 6', 43 gal. Gas tank usually run 20 gal. Of gas, 20 gal. Live well, 2 batteries, 2 adults, I usually fish 8 months out of year. Boat is used in New York : jamacia bay, New York bight area. I rebuilt the transom for a 25"shaft four stroke engine 150 h.p. Yamaha, I would like to know if anyone can recommend a propeller size/pitch to get the boat to do 40 - 45 m.p.h. If not with 150h.p. Then perhaps with the 175h.p. Yamaha..