Prop pitch on a pontoon?

[MuskieJunkie]

Anyone have any recomendations for the pitch on my mother-in-law's Mercury 60hp 4 stroke on a 22' Pontoon?

The motor originally came with an 11, TnT Marine in Grand Rapids sold them a 12 and now it sounds like it's not getting up to the full RPMs (no tacometer). I'm thinking of trying a 10......

[vermilionfox]

How did the 'toon do with the 11 pitch prop?

Dropping 2 inches in pitch may be too much for the motor.

Is this on a 60hp Bigfoot motor? If so you need to keep an eye on diameter too. The Bigfoot swings a larger diameter prop.

Get in touch with Soderbloom's up near Duluth. They're a sponsor on here and really up with it on their props! Do a search, you'll find them.

[MuskieJunkie]

That's a whole nother thing - there were some issues with the 11. At 3/4 throttle it was fine, at full throttle the motor would rev high and the boat would slow way down, stall I guess. Different trim angles didn't help.

I thought it would have been an issue with the motor mount but I don't know, the marina said the prop was spun and replaced it (with the aforementioned 12 pitch).

What I don't get is the prop functions fine at 15 mph but when you try to go 20 mph it slips??? That doesn't sound right to me, I would think if it spun the prop would slip at any speed....

If anyone can shed some light on this I would really appreciate it.

I don't think it's a bigfoot.

[broken_line]

sounds to me like cavitation.. can you lower the motor further into the water?? if not you might want to look at a hydrofoil not really ment for a pontoon but will help with cavo... about 15 mph tooners get on plane and lifts the motor further outa the water and your wake from the toons will converge right behind the motor thus allowing alot of air..

[marine_man]

I was thinking the same thing... sounds like your prop is too flat... or too low of a pitch.

marine_man

[MuskieJunkie]

Thanks for the input.

So it's highly unlikely that the prop is spun right?

[marine_man]

If you're seeing similar issues on two different props, under approximately the same conditions, and it doesn't happen right away, I really doubt that it's a spun hub.

But, to check it, pull the nut and washer off the back of the prop and take a paint stick and draw a line from the outer portion of the prop, across the hub to the inner splined portion. Take it out and run it, and take a look when you get back to see if the lines are still aligned.

marine_man

[MuskieJunkie]

Great tip, thanks Marine Man.