correct pitch for yamaha f40 pontoon app

[LEGENDRIDER]

Hi all,

Just curious to the correct prop for my Yamaha F40 which os on a 18ft pontoon, I suspect the one we have is not correctas it only reaches about 3900 rpm at WOT

Thanking you in advance

 

[Silvertip]

Re: correct pitch for yamaha f40 pontoon app

What pitch is the current prop. Engine running OK? Did it ever rev beyond 3900?

 

[hwsiii]

Re: correct pitch for yamaha f40 pontoon app

Legend, we welcome you to the forum and hope to be able to help you with the questions you need answers to. If you will supply us with the answers to the questions listed below we will have everything we need to help you with your quest, in most cases.

Boat and Motor

H

 

[steelespike]

Re: correct pitch for yamaha f40 pontoon app

Prop size usually appears on the barrel or under the prop nut.
A one inch reduction in pitch will increase rpm ABOUT 200.
Assuming the max rpm of the F40 is 6,000 you would need about a 10"
reduction in pitch. If your allready at say 15" You have other problems.
You may still need a prop reduction but the motor may need a check up.
If you can get us the prop size,and max rpm and speed we can tell better
whats up.

 

[Silvertip]

Re: correct pitch for yamaha f40 pontoon app

A 40 four stroke on an 18 foot pontoon should do well with a 14x 11. If you have a prop in that range, there is something wrong either the boat or the engine. Even a 60 HP 4S runs a 14 x 11. My 18 foot Misty Harbor is powered by a 40 Suzy 4S and it runs an 11 pitch at 5800. I would start by verifying that the throttle linkage is adjusted correctly and that it is opening fully at wide open throttle.