another prop question and advice

[edthearcher]

I have a 1986 sea ray pachanga rebuilt engune 5.7, alpha one out drive also rebuilt, boat dry weight 3,000 lbs, 63 gal. tank 3/4 full the alpha 1 gear ratio is 1:50 -1 manual says max. RPM is 4200 to 4600 prop #1 j15X17 4900 RPMs 47 mph, prop #2 14.5X19 5000 RPMs 48.5 MPH all test using garmin GPS first test I was alone, 2nd test my wife was with me, both test WOT trim lower unit to get max. RPMs. I have been told I should get over 60 MPH out of this unit, need advice on what prop i should go to, also both props are alum. I forgot to mention its a 22 foot

 

[steelespike]

How was the hole shot with each prop?
Slip with sa 17" was 10% ,19" was 19%
Assuming the motor could turn it you would need a 23.5" pitch at 4600 rpm.If your turning 5000 with a 19", if we call it a 24" prop it
would knock about 1000 off the rpm so 60 doesn't seem likely at this point.While not carved in stone the the 19" should turn about 400 rpm less that the 17.
It's possible the tach is wrong or perhaps the 19 has a problem.