V20 with Black Max 150???

[bigshrimpin]

Originally Posted by randymbtech

Hey guys, I'm new to the site, just bought a 1983 V20 cuddy with a 1986 Merc Black Max 150.

I'm trying to get the prop size right. The boat came with a beat up aluminum 19 pitch prop, and it performed terribly, so I bought a used Mercury Mirage 17 pitch stainless wheel. I am impressed with how it spins the Mirage. It comes out of the hole great, but the RPM's are too high at WOT (over 6000 RPM). It will do only about 36 MPH at WOT. I would like to be able to cruise at a lower RPM, so should I move up to a 19 pitch Mirage? I thought that the 19 Mirage would be way too big, but it seems to spin the 17 too easily.

Thanks in advance for any advice.

Randy

Randy - IMO the 17P mirage plus is probably a very good for you, but your tach has to be wrong . . . unless your are sucking a lot of air . . . your slip would have to be more than 20% to turn 6000 with 2:1 and 17P and only achieve 36mph. GPS's don't lie. You can run the numbers and see for yourself.

http://www.go-fast.com/Prop_Slip_Calculator.htm