Pontoon Boat & Deck Boat Forum

I found a few threads on how to calculate slip but not any stating what is an appropriate amount.

If my calculations are correct my prop slips 46-50%. I measured speed (iPhone gps) at 1000. 2000, 3000, 4000, 4200, 4400, 4600, 4800 5000 & 5200. Boat was loaded heavy for me - full on gas, 5 people 3 ice chests, 2 dogs and camping gear.

Boat is a 22' Bennington with a '99 merc 115 2S. Prop is a Ballistic 15P. Top speed at above conditions is 19.5mph. Two people and quarter tank runs 23 mph. Same 5300 max rpm loaded or unloaded.

Too much slip? Would I benefit from a different prop?

23 light and 20 loaded with a 16 year old 2-smoke does not sound too bad for a 22 foot boat... Keep in mind that the slip charts you will find were likely not built up around a pontoon boat but more than like a traditional planing hull. Pontoons will always have much higher slip rates.... Do you have a spare prop? If not here is your excuse for one. For well under 100.00 you can find brand new alum 3 blade props to which I'd look for one with 1" less pitch to try out. Your results will either be better or worse but it will not be much different and either way you've got a good 2nd prop as a spare.

gobeernet wrote:... Same 5300 max rpm loaded or unloaded ...

This is the part that makes me curious about a new prop. I figure if I'm tached out heavily loaded, then I can go to a higher pitch or prop with less slip to gain higher cruising speed.

The last few weekends we have traveled 35-60 minutes one way to our destination. I'd love to bring that lower for passenger comfort and gas.

Seems like too much slip IMO, and the Ballistics prop isn't a good pontoon prop with its smallish blades and higher rake. A twin tube should be able to achieve slip under 30% with a proper prop. A Mercury Spitfire 13P is where I would start, should be good for 23-24mph @ 25% slip and maybe faster since it will have quite a bit more bite on the water.

At WOT I am getting 24% slip. I run a stainless (cupped) 14x13 prop on a Yamaha 115 4-stroke. Its a 24ft two pontoon with no strakes. This is with a small load. Top speed is 25 mph at 5700 rpm.

I've worked mine down to 12%, took 4 or 5 props and bit of trailing edge tweaking. You see can the difference in fuel use, speed and hole shot.