prop question

[Steven Ard]

I have a 16 foot pontoon boat with a johnson 40hp.<br />the prop is a 12 1/2 x 13. At WOT the tach reads 4400 rpms with the wind at my back. What prop would I need to achieve the recommended WOT rpms.<br />Im not 100% sure but I think it is supposed to turn around 5000. Load is usually 2 people and light gear.

 

[Steven Ard]

Re: prop question

its a 1991 model tracker 16 foot pontoon with 1990 or 1991 johnson (tracker) 40hp

 

[Moody Blue]

Re: prop question

General rule of thumb is 1" reduction in pitch results in 200 RPM increase. Following this logic, you would require a 10" pitch prop to achieve 5000 RPM.

 

[Steven Ard]

Re: prop question

thanks for the info. Just looked it up and 4500-5500 rpms is the proper specs. Im not as concerned about hole shots as i am top speed. pontoon boats aren't exactly know for breaking speed records. But mine wont even blow the hat off my head. Any extra speed i can get out of it would make my fishing days better.

 

[Bob H.]

Re: prop question

You may want to check the Michigan Wheel catalog since it will give you a ballpark recommendation based on the hull configuration and weight. Smaller pitch will raise rpm's but you may not like results at slower speeds having to move that load with less low rpm thrust, especially if there's a breeze. Some prop shops let you test drive their wares.

 

[moderator1]

Re: prop question

I've seen alot of toons with the engine mounted way too far down....this could be another.<br />A good 10P would be a good starting point...just because we lower pitch doesn't mean we lose speed.<br />At 4400RPM, that engine isn't even reaching it's rated HP....5000RPM is better, but mid 5's would be best.

 

[WillyBWright]

Re: prop question

13 is for runabouts. 10 or less for toons. Did the dealer stick you with that 13? Shame On Them!

 

[Steven Ard]

Re: prop question

I bought the boat from an individual, but it had less than 20 hours on it when i bought it. I would assume the dealer did set it up with the wrong prop. I am gonna try a 9 I think

 

[Steven Ard]

Re: prop question

Michigan wheel says to use 12.25 X 15. Wouldn't that lower the rpm's and slow it down more?

 

[roscoe]

Re: prop question

Yes it would. Don't do it.

 

[moderator1]

Re: prop question

Double ditto on the "Don't do it"...

 

[Steven Ard]

Re: prop question

I think I'll try a 9 or 10. Thanks for all the info.