Offshoreonly.com - Is a prop slip of 7-8% realistic?

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I've also been eyeballing the bmax outdrives. I here they are pretty stout. I keep thinking my bravo ones are going blow if I ever get a chance to hammer it

Quote:

Originally Posted by t500hps (Post 4586277)

After prop experiments I went from 18-19% to 10.5% in a 382 Formula......and 10 hours later trashed an outdrive. Slip isn't always a bad thing :(

Quote:

Originally Posted by veloc410 (Post 4586392)

T500 .Is that a fountain. I see step transom. How far below the deadrise are your propshafts??

2002 Formula 382. Don't know X-dimension but it's standard XR's from the factory w/o stand-off boxes. I did try a set of cut down 15 1/8 Bravos and found in a chop they would "blow out" on one side very easily because the blades were too short.

Whoops you did mention that earlier. I saw stepped transom on your avatar

Quote:

Originally Posted by veloc410 (Post 4586425)

Whoops you did mention that earlier. I saw stepped transom on your avatar

No problem........that pic was taken several years ago and the last time I saw it (new owner was hauling her away)

Quote:

Originally Posted by Warship2k15 (Post 4586348)

Sometimes slip numbers are wrong.

example:
I switch from one 25 to another.
my slip numbers go down from say 13 percent to 9 percent.Looks good on paper but if my new prop actually has 26 instead of 25.Or my old one was actually 24 instead of the 25 it said then my slip numbers are almost identical to my old prop.

The slip is not wrong, the data you input is incorrect.

Quote:

Originally Posted by Sonic24 (Post 4586174)

Is a prop slip of 7-8% realistic?

We recently tried a new prop and got significantly better performance.
Our previous props were producing 16-19% slip (24 and 26 Bravo I props. 24, 26, and 27 Hydro props)

Then we tested a 21 Pitch Revolution 4 prop, 7% slip!
It is such a dramatic difference, I have to question the results.

Boat details:
1993 26' Velocity
Bravo XR 1.5:1
new 21 Pitch Revolution 4 (LH)
new tach 5700 rpm
2 independent gps showing 70 mph

Completely realistic, particularly with the Rev 4. Large diameter and large blade area equals lots of water moving. I'm at 5% with a Rev 4. The best I've ever personally recorded was 3% with a Mach Sterndriver at cruise speed.

Remember slip is not constant, but varies greatly through out the RPM band. At idle to before on plane slip is typically 30-50% or more. Trim angle will also impact slip. Get a prop that performs the best with the hull, reaches the motors appropriate power band and has minimum slip.

My twin formula is around 9% wot with mirage + props. Same prop on my smaller single formula is about 15% wot.

I'm getting 30% at 40mph a little under 25% at 60mph faster I go less slip