prop question on 3.7

[926bill]

Aussie, I run a 14.5" X 19P. It's a 1983 v20 170hp 470 mercruiser. With a full tank(60 gal), two people and fishing gear, coolers, ice etc. I can run 34mph-gps at 4200rpm. That's on a dead flat lake Erie, which we don't see very often. I've never taken her beyond that but it still has some left, just no reason. I cruse at 3200rpm 24mph gps in a 2ft or more chop, I've found this to be the most comfortable ride without beating myself and the boat to death.
The mercruiser manual says 4200-4600rpm max. These motors have alot of torque and on lake Erie when you get into 3-5 ftrs that means boat control.

BC