Re: 3.7 mercruiser prop size
Definately a Michigan Wheel 19 pitch x 14.5" diameter.
No seriously, how in the world could we know? Wait, I am guessing that since you actually bought a boat with a 470 in it, you know very little about boats. Cause if you knew about boats, you would have known to stay away from that engine. That said...
Most boats get anywhere from a 17p to 21p prop. I don't know why exactly, they just do. You can't always chose a diameter, either. Some manufacturers just make one diameter for each pitch.
As noted above, you need a baseline, and only then can we help you figure out what you might need.
Good luck.
