Trying to get prop slip #'s down

[J.Pedalino]

First post in a while, maybe ever, but im trying to get my prop slip % down

I'm running a 97 Gambler 209 with a 2021 250 proxs. 12" of setback from a 10" bobs with 2" spacers. 26p trophy turning 6100 at 75mph. Also ran a 26p bravo1 at 72 with 5600rpm, a 27p trophy with the same rpm and speed at the bravo. Playing with the jackplate and trim angles until I loose speed or stability has helped me find the sweet spot and these are the best numbers I can get. Consistently 11-12% slip on all 3 props in various water conditions and temps. Ive ran 10" of setback and had 1-2 mph faster but stability was out the window. Thought about trying it again, also have some 4" setback plates I need to re drill so I can give 14" of setback a try. I still lack some serious experience and would like to hear from more experienced people about what other courses of action I can take.

Thanks.

[David]

Those are not terrible slip numbers. Oddly enough I did some rpm vs mph testing with my Allison SS2000 this morning and got 6-9% at different speeds. But I have a lighter faster hull, so less slip would be expected.

If you are not using a ton of trim and have a big roostertail, your set up may not be far off. Is 72-75 about what one one expect with your boat and motor? Which prop gives the best acceleration? Do they all handle the same?

[OnPad]

As David said, your #'s don't sound to bad.Probabably better than my 20' bullet with a 26p trophy.
Some props I would recommend are full size trophy, tempest, bravo xs, or signature eagle 4. Dependent on whether you have a nosecone or not, and engine height (p.t.p.)??
In my experience engine height and diameter of prop make the most difference in slip #'s.
Also, bravo props tend to run a bit light on pitch, compared to others.

[NZ Sidewinder]

Those slip numbers are okay IMO.
However, I'm not an expert in props by any means although I've just has an experience that taught me a lesson.
30hp mini racer running a prop that was way to big.
21inch pitch, 11inch dia. (Cleaver)
That's a big prop even if the shaft is at pad level.
It ran 5900rpm which is a hell of a lot for a stock 30hp Parsun with that prop.
I put a 18inch x 11inch cleaver on that had been worked nicely on the leading edges and had a decent cup.
That prop ran 5400rpm and 3mph faster.
So there was something wrong with the big prop and by comparing the two closely the answer seemed clear.
The big prop had a very crude leading edge and no cup to speak of.
The blades were flat to look at.
The leading edges were rubbing the water and overall it was plain to see that it was a dog.
So the lesson to me was that there are props and there are props

[Capt j]

I'd try a 26 or 27" promax propeller. Although the bravo XS is a much better all around prop. A 26" bravo xs might be the way to go.