Prop for max speed on a 75 Merc

[goat32eaglecap]

I recently bought a pontoon boat with a 75 hp Merc and it's slow, and I was told a stainless prop would help? Any help or advice?

 

[jimmbo]

What is slow, mph wise? What rpm are you currently getting and what prop currently on the engine. Also needed is the WOT rpm range for your engine. Also to consider, is the motor mounted at the correct height for a Pontoon. Oh yeah, you never mentioned any info about the Pontoon, as in size, weight, max HP rating, and what your intended uses are

 

[Scott Danforth]

with pontoons, you must get the motor height correct. a pontoon boat really needs a powered jack plate

if your prop is too deep, you increase drag and loose efficiency. if its not deep enough you get blow-out

once the motor height is correct, you can move on to prop

there is a sticky at the top of the prop forum. need the answer to all 6 questions.

 

[Sea Rider]

If OP is new to boating he won't know what we're talking about regarding lower leg drag or prop aeration OB related. To make it simple, with OB trimmed to neutral, deck weight evenly distributed go full throttle on calm water cond and visually check by pulling head out transom at which lower leg is water flow passing by at speed.

Ideal lower leg height will be when water flow passes at speed right under small upper water deflector plate, raise or lower OB accordingly till that cond is met, Once at the correct OB height check with a tach max achieved wot revs as usually loaded. Need a 3-4 blade prop that makes the OB to rev middle to max wot rpm range factory stated although max rpm is preferred to be on the way faster.

If OB is way under powered for that size toon will achieve only nice fast displacement speed while OB revs happily at wot..

Happy Boating