what is a realistic prop slip for a late model 42 Lightning?
 

I have never been able to get better than 20% with 700's, #6 drives and 6 blade Herrings. 16% was from the factory report. Either everyone else is BS of something is wrong here.

Gear Ratio Pitch RPM Theoretical Speed Slip Actual Speed
1.5 37.5 5350 127 16% 107
1.5 37.5 5550 131 20% 105
1.5 37.5 5800 137 20% 110

Maybe your 37s are really 35s ?

Who cares ,,if u run the speed u want ,,the slip is really not to worry about .

My boat has 24 with my big wheel and 16 with my small prop,but it runs the speed and that is what counts .
All depends on drive hight and gear ratio as well.
Fountain raceboats have like 30 % slip !!:eek:

Everybody is worried about slip # ,,,,WHY ???:party-smiley-004:

Isn't slip wasted HP, gas and speed? Slip is caused by parasitic drag from everything touching the water. Improving the hydrodynamics of those items would reduce slip and increase speed and MPG. I would imagine some slip is good for reliability like in and out of water shocks. It also probably helps performance like a stall converter by letting the engine rev a little quicker to get to the power. What is a desired reliable/economic/performance slip number to aim for?

It all depends on the boat . The way i see it is if your happy ,,don't mess with it and the slip is theory nothing more.
A good and fair # would be 12-15 % on a v hull.
But like i said before ,,speed counts and if u have slip,,i don't think u would notice the HP loss or the MPG deferents .

Slip #'s are great tools. The tool is sometimes over valued in my opinion. Sometimes the only way to achieve the highest speeds is with higher slip numbers. Harnessing the slip could actually slow you down. This is most often true with true V hulls.

This being said, I'd like to see these boats running at 16% or a little less. Most often the aggresive X dimentions on Fountains can cause the high slip #'s. Great for light load racing but not great for family boating.

B

All things being equal, lower slip raises the top speed. The props are Herrings and the boat was supposed to be dialed in at the factory. The test sheet is 4mph higher than any other 42 / 700 package I have seen, but when I bumped the power, it started slipping a lot more. 4-5% is 5-6mph at these speeds and we all know how much one mile per hour costs at this level. Either I am the only one out here with accurate test equipment (data logging from my Rhinda) or something else is wrong.