20’ Pontoon pitch

[Stubrown12]

Recently purchased a 20’ pontoon with a 40 hp. Switched to a 75hp Mercury. The pontoon will run 18/19 mph on a 19 pitch three blade prop only turning 4000rpms. What pitch do I need and 3/4 blades. Thanks in advance.

 

[Faztbullet]

3 or 4 cylinder 75HP?

 

[WesNewell]

A rough guess would be a 12p 4 blade. Try the mercury prop finder.

 

[ahicks]

2 stroke or 4 stroke engine?

3 blade if speed is your objective, 4 blade if max thrust is the better plan.

19p obviously way to big.
Our Honda 90 on our lightly loaded 24' toon likes a 15p 3 blade (5500/26mph), or for neck jerking hole shot (pulling), a 13p works good (6100/24mph).

A similar 75 on a lightly loaded 'toon should work good with one of those props, or maybe with an inch less pitch. Noteworthy maybe, is that the 4 strokes sound kinda busy when run at max rpm (6000). Sound MUCH better and are sometimes faster when set up at 5500.

 

[Stubrown12]

3 cylinder/2stroke

 

[Stubrown12]

Wanting to pull the kids. Maybe try skiing

 

[ahicks]

You may be OK with smaller kids on skis, but I would plan on lots of tubing.

I'd be tempted to try an inexpensive (Solas) 13-14p alum. 4 blade with the idea it should be close. You may end up having to buy a second prop to nail it.

 

[Starcraft5834]

ive got a 20 ft toon with a 115 4 stroke on it. got a 15p 3 blade on it