Prop Slip Calculator Question

[idvette]

I was doing a little "bench" testing with my setup. Through 1.87 gears, a 30 pitch prop with engine RPMs at 7000 one would theoretically be running 106 mph. Factor in 10 percent prop slip and it's still well into the nineties. Is that what I could expect from my boat? How accurate are these calculators, and what's considered acceptable slippage? What factors affect slippage? Not a chance of me seeing those speeds any time soon, just curious what she's actually capable of, real world. 7000 rpm may be a little ambitious as well, the fastest I've turned the motor so far (besides trying to get up on plane) is about 5500, as my steering locks up and I don't have the stones to try to go faster with no steering lol

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[transomstand]

Prop slip calculations are a tool to see where you stand, and to measure improvement in your setup, BUT, all slip calculations are "theoretical". I rarely use one, and can't tell you what my current prop slip even is.

I use an alternate method....If I put up a big number on the GPS, prop slip is "good", if I get a low number, prop slip is "bad"

[silkeysak]

Prop slip calculations are a tool to see where you stand, and to measure improvement in your setup, BUT, all slip calculations are "theoretical". I rarely use one, and can't tell you what my current prop slip even is.

I use an alternate method....If I put up a big number on the GPS, prop slip is "good", if I get a low number, prop slip is "bad"

Great answer!
To reduce slip you can add cupping, but it also increases "theoretical" pitch, using the esteemed" transomstands" terminology. I also bet he knows exactly what his slip is. It's how far you slide on the boat ramp! It also sounds like you have no feedback steering, causing the "lockup". Get rid of it, and your stones will get instantly larger!

[idvette]

I have a ride guide setup on it's way, probably won't be installed until next year, so I'm keeping the speeds down until then. Just going to play with it, get a good feel for the hull, then hopefully when I really lay the sauce to her I'll already have an idea as to what she'll do lol.... I did see somewhere around 80mph a few weekends ago, I saw the speedo sweep past 70 and I still had my foot in it for another few seconds. The boat handled great, but since I couldn't steer, or correct if I got into trouble, I backed out. I was watching the lake more than the guages at that point. The amount of throttle I had left really got me wondering what the boat actually was capable of. I know the speedo isn't the most accurate, I should get a GPS, but it had me pretty excited over what may be....

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