Pontoon Boat & Deck Boat Forum

trying to get to my desired wot rpm on my pontoon,its a 32 ft party cruiser but its heavily modified ,it has a third toon and a 250 optimax, ive started with a 15x17 and got 4700 rpms ,16x13 prop got 5200 rpms,trying to get to 5700 wot rpm,all the prop calculators wont work and guessing is getting expensive,i understand dropping pitch 1"is 200 rpms less but should I go less diameter as well ? and no I am not making a speed boat I just like to have the power in case of emergency,thanks in advance...and spare me the speech about these mods to the boat aren't legal. thank you

First I would suggest a Mercury Enertia prop.
Now for size, either a 15.3X14 or 15X15 would be my guess.
I personally run a bigger prop that slows my max RPM down, in my case it saves GPH and raise top speed.

Gosh, you've got a rig that I've never seen anything close to. You should go down on the pitch, and a motor of that stature deserves a stainless prop.

Is there a dealer that would allow you to take 3 Enertias to the lake and return two that don't perform well? What's nice about that prop is that it comes in 1 inch pitch increments.

This might be one of the few situations where a 4 blade prop may be required. You might want to talk to one of the mail order prop guru's that people talk about online--like PropGods.

[quote="kenbob62"]i understand dropping pitch 1"is 200 rpms[/quote]

In my testing of a Mercury Enertia prop, 1" change of pitch was close 400 rpm change.
Also, check out this site.
https://www.mercurymarine.com/en/us/pro ... #/step-one

I have a slightly used Enertia 15.3 x 14 for sale in the Buy/Sell forum here
used about 3 hours with hub kit for 450.00 shipped to your location

Mike

thanks for the replys,i put a 16 x 11 prop on and hit the wot rpm perfectly

[quote="kenbob62"]thanks for the replys,i put a 16 x 11 prop on and hit the wot rpm perfectly[/quote]

I bet your hitting your rev limiter with a 11 pitch and it appears to be perfect.
As long as your happy, enjoy.

im hitting 5600 rpms at WOT wich is perfect and never hitting rev limiter, with a 2 stroke if you don't have it propped correctly you risk premature engine wear. when I finish welding the strakes on I might have to change props again, this boat is 32 feet long and heavy not aerodynamic at all. we can cruise at 20 mph and we no longer get passed by every dam boat on the bay and have to eat their wake.

what does the light in the prop do? mine doesn't have one.

[quote="boocat"]what does the light in the prop do? mine doesn't have one.[/quote]

Someone please fix the "Big Grin" smiley...

[quote="DWRAT"]First I would suggest a Mercury Enertia prop.
Now for size, either a 15.3X14 or 15X15 would be my guess.
I personally run a bigger prop that slows my max RPM down, in my case it saves GPH and raise top speed.[/quote]

This will eventually damage your engine (especially at higher rpms), with too much pitch you will have a higher top end, but your engine is lugging to turn the prop, think of a car with a manual transmission, and starting off in third gear, normally you will hear pre-ignition (pinging). when your engine can develop the top range of it's intended RPM then that prop is well suited for the boat and motor, and will perform correctly throughout all RPM ranges. we don't run WOT for extended periods, but when you are testing props the boat should have a normal load onboard and reach the MFG Top end of RPM range (normally 5500 - 6000).