How do you calculate speed and prop slip?

[Tom Slick]

Hey guy's,
What is the formula used to calculate speed (MPH) and prop slip?

[FASTERDAMITT]

Try this sihttp://www.go-fast.com/BOAT_SPEED_PREDICTIONS.HTM

[riverliver]

www.boatpropellers.com (http://www.boatpropellers.com)

[Infomaniac]

Cannot calculate slip. Way too msny variables. Need to calculate the speed then measure it with a GPS. The difference will be the slip. Once you know the slip you can accurately calculate speeds with different props, RPM etc.

[HavasuDreamin']

Formula is this:
1. Take RPM and divide by gear ratio.
2. Take result from #1 and multiply by propellor pitch.
3. Take result from #2 and divide by 5,280 then again by 12.
4. Multiply result from #3 by 60.
5. Multiply result from #4 by .9 for 10% slippage.
http://free.***boat.net/ubb/cool.gif

[FastCats]

Thats good stuff Dreamin, But for accuracy, be sure to remember to call a 32p prop a 31p because of it being a 4 blade or a 28p is really a 27p, etc...