What is the formula for prop slip

[Mike Cork]

Just to get it on the board for everyone to use, how do you figure prop slip?

And is there a general number we all should shoot for, or is this boat/motor specific?

[HOLESHOTPROPELLER]

Go to Mercury racing .com/prop slip calculator..less than 10 is good

[hughesjasonk]

http://www.mercuryracing.com/prop-slip-calculator/

[HOLESHOTPROPELLER]

Lighter faster boats have lower slip numbers than big heavier boats mostly because of weight

[merc1997]

here is the formula to figure speed.  rpm time your pitch, divided by gear ratio, divided by 12, divided by 5280, times 60, times .9.  this will be, most of the time + or - 2 mph of what you are actually running.  for those with gps, you can also tell how much your prop is slipping.  even with bigger boats, you can improve the prop slip by getting the right wheel on your rig and tweaking it.

you need to shoot for 10%, and if you can get down to 8%, you are pretty much as good as you will get.

one might ask, why go to all the trouble?  it translates into fuel mileage.  so, if you fish much, over the course of time, you will more than pay, for the extra expense of finding the right prop for your boat and getting it tweaked to get the mos out of it.

bo

[Bigwrench]

Don't forget the free apps if you have a smart phone also.

[merc1997]

using that formula and checking it against your gps speed will give you a pretty accurate gauge to actual slipage.  so, if you do the math, and your gps speed is more that the math speed using a 10 slip factor, then you have a good prop setup.

bo