Need to look at RPM of the engine at full speed.Compare that for the manufactured published allowable rpm specs of your motor.There’s a rule of thumb often used that says each inch of pitch is generally worth 150 – 200 rpm.Lowering the pitch increases rpm and vice versa. So, for instance, if you were to lower from a 23-pitch to a 21-pitch propeller, you’ll increase engine RPM by about 400 revolutions.4 blade props give you a better hole shot but you sacrifice top end.Stainless props are stiffer than aluminum, so they resist flexing.A thinner stainless steel prop spins up quicker and will attain a higher rpm vs an aluminum because of this.So a stainless steel prop will out-perform an aluminum prop both out of the hole and at top end.However, there's tons of guys that won't use a stainless prop for fear of damaging the lower unit or motor if they hit something with the prop.All things to consider.Good luck
RPM on the motor when I trim it out, fully loaded with 5 people and my gear and dog, I get the 6000 rpm that they say I should be getting. The boat gets on plane right now, pushes you back in the seat. Just seems like everyone I talked to said they usually get about 45 mph out of their boats, I know not mine, but figured it was worth a question, plus I always learn something new from these types of questions. As I am one of those guys that tend to stay away from stainless props but now understand the reason that some really like to run them, I just seem to hit things from time to time and would hate to kill my lower unit and then have to pay to repair it, but I guess hitting something might do that anyways.
GPS speed on my fishfinder is say 36 mph. But just got through the 2 hour break in period and starting on the 8 hour one that I can run full throttle for 5 minutes before I back out of it. Have the tilt and trim on the motor and use it like my old boat. I got 28 to 31 out of the 90hp on an almost 18 foot boat, granit that it was a side console and this one has the full windsheild and is almost 20 foot long. Like I said just seems a bit off for top end for me. Thanks so much for all the great information everyone.