HALLETT FAN

Before engine mods, running a stock Bravo 1 28p at 5100 rpm my slip calculated to 10%...good . Now after putting supercharger on, I can do 96mph at 6200 rpm which equates to 18 % slip, with a Bravo
1 30p prop... why the dramatic slip increase ? Boat is Hallett 270
with 2 step hull, imco extreme drive with extender box...

HALLETT FAN

Anyone? Bblades ? Throttle up ?

Griff

Probably going need to go to a 5 blade prop.

docmanrich37

Your slip is actually 15.4%.You have to make the 30 pitch in the calc. a 29.Is the prop a box stock?

HALLETT FAN

Yes , it is a stock Bravo 1

bbladesprops

Your slip most likely is in the 16% range.

First, different propeller pitches in the same family with same geometry have natural efficiancy changes. Did that come out clearly? Sometimes I don't write exactly what I'm thinking. (However, this pitch, 30 B1, should run very efficiant.)

Secondly and most important, boat hulls change their running attitude as speeds increase. It is easy to understand this if you concider the wetted surface area of your boat at 40mph vs. 70mph. As the boat lifts, so does the propeller. As the prop reaches the surface, many things can happen. Ability to hold the bow can lessin, induction of surface air can be enhanced. The personality of each different propeller is shown at WOT (those are important words) ((don't tell any one)).

So, leave well enough alone, you are going faster. Slip % can be over rated. If it takes more slip to go fast, slip away!(this is a whole other thread). Test with 1/2" spacer. Try multi blade props.

If you want to talk about this more, don't hesitate to give me a call. Anytime.

As my New Zealand friends say,

Cheers.

HALLETT FAN

Thanks , Bblades, that make sense. Maybe for all out ultimate speed
a five blade ...

bbladesprops

If you want to test with a 5bl Maximus, let us know.