I'm getting some very high prop slip numbers with my boat. I've got an '87 Formula 242 with a built 427. The engine was supposed to be around 550 hp but I'm only able to spin a 21 Mirage at 5700 rpms. At that I'm getting 57 mph which gives me around 26% slip which is much to high. The bottom has old nasty, rough bottom paint on it which I'm in the process of stripping off but I'm I really loosing 10 mph and getting the high slip number due to the paint?

Sounds about 10% too high to me but I'm not an expert.

i think yes

Call Bill at Propshop 800-338-8900 in algonac Michigan he has 30 Plus years exp.
I called him 4 years ago on my cat he set me up tith a prop for $400 off the shelf it was out of this world.
So I bought a 38 Cigarette and had the same prop slip as you 26% so He set me a set of props and was telling me about hub emersion or whatever, he lost me with his knowladge. I ran them yesterday. GPS the boat and put in the Drive gear, Mph I was getting and Rpm on the proslip calculator and I picked up 12 Mph and my proslip went to 14% and running 68 Mph on a 10k pound boat.
If you get a custom prop youll spend over $1000 to get 2 more miles per hour than what he sets you up with.
Justin Osen.

i think the combo of bottom paint and the 3 blade prop are slowing you down

Thanks guys.. I got the bottom paint off and I gained a solid 5 mph and dropped 5% in prop slip. But now I have a fuel issue. I've got a new pump coming tomorrow so hopefully I can start messing with props again. At least now I can easily get on plane with my labbed 25 mirage plus. With the bottom paint it was impossible. Nothing like bunk carpet in the paint to slow you down.

Bottom paint is always a deterent to performance. Older 3 blades props didn't have the same cup specs. as the newer ones and could have higher slip numbers. Also in time what cups are there can be washed out and blades can lay back causing higher slip nubers.

If you want to try some different propellers, we have a wonderful test prop program.
http://www.bblades.com/pressreleases...essReleaseID=3

Thanks,
Brett