Pontoon prop help

[dd8769]

I have a 24 foot fisher dlx 3.0 alpha 1 16*11 prop 20 mph 3000 rpm wot any suggestions would be appreciated

 

[lncoop]

Re: Pontoon prop help

Those RPMs sound low, but no one will be able to help much without knowing what your prescribed range is. FWIW I've learned you can expect to add around 200 RPMs for every 1" decrease in pitch.

 

[dd8769]

Re: Pontoon prop help

Manual says between 4400 and 4800 thanks

 

[rutcutter]

Re: Pontoon prop help

Under normal load your wide open throttle RPM's are way low. You need to decrease the pitch on your prop substantially. A 1 inch decrease in pitch will raise your wide open throttle by about 200 RPM.

 

[lncoop]

Re: Pontoon prop help

A mathmetician I definitely ain't, but based on the numbers in order to get to optimum RPMs you'd have to drop to a 3 pitch prop. That of course is a ridiculous notion, so it sounds like you may be having issues other than prop pitch, like a flaky tachometer or motor issues for instance. Sounds like you've got some investigating to do.

 

[Racerjoe56]

Re: Pontoon prop help

Please note the outcome as I have very similar deal. 24 foot Fisher DLX 3.0 135 and WOT with 11P of only 3200 (recomended range is 4400 - 4800) Not wanting a speedboat as I have one of those - just want to get out of the lightning quicker if need be.

 

[Silvertip]

Re: Pontoon prop help

DD -- you have a number of possible issues, none of which are related to the current prop. 1) the tach may be inaccurate. Check it with a shop tach. 2) The throttle is not opening fully. Throttle blades should be standing straight up with the throttle full open. 3) The tubes are fowled with marine growth. 4) The engine is in dire need of a tune-up or is simply tired and in need of rebuilding. If the engine is only turning 3000 RPM at WOT then you need to make up 1800 rpm. At roughtly 150 - 200 rpm per inch of pitch you would need to drop about 9 inches of pitch leaving you with only 2. Does that sound logical?? I sure hope not. Better do some diagnostics before spending money on props.