what is the best slip # we look for

http://www.go-fast.com/prop_slip.htm
http://www.go-fast.com/boat_speed_predictions.htm

old school thought was ..........

under 10% for race applications
10-15% for sportboats
15-20% for planning hulls.

There are specifics for every set up though.
If you have a slip in the 11,12,13,14 range you are most likely fine.
Under 10% slip for boats not designed for or dialed in specifically for is rare.
Often gages and numbers used for input are skewed.

Brett

Thank you Brett

Awesome, now I know that my 38 Lightning is a "planing" hull. lol

And of course... apps for the iphone...
Prop Slip - https://itunes.apple.com/us/app/prop...459768648?mt=8
Boat Speed Calc - https://itunes.apple.com/us/app/boat...466829842?mt=8

Low slip #'s not always best.

Your boat is telling you what it want's - are you listening ? LOL.

There is so much truth to this!
Some of the fastest top speed we have achieved on any given hull may be with a higher slip number than we anticipated or had had. In other words, we had 10% slip and ran 78mph. Ended up with 15% slip and ran 81.
Deeper V's are known to do this.

Brett

How about for cats packing air with high x?

Lower slips are definitely more common.