Need prop size advice

[JohnOD]

Folks I need some suggestions as to the proper replacement prop for my fishing boat. I believe I am currently overproped as the hole shot is sluggish and the tach reads 4800 max @ WOT. The top speed is fine, what I want is to be able to get on plane more quickly. Last weekend I was running 29 MPH with me, gear & a full tank of fuel. I added two additional anglers and a heavy cooler and could not break 13 MPH.<br /><br />I suspect that the dealer I purchased the new baot/motor/trailor package from this spring did not make much of an effort to get me propped correctly.<br /><br />Here are the particulars…<br /><br />The boat is 17 ½’ aluminum North River revenge which is rated for a maximum of 60 HP.<br /> http://www.northriverboats.com/models/all/specs.php?productid=5 <br /><br />Honda 50 HP tiller 4-stroke currently with an aluminum C3x11.1x14 factory prop, Hondas recommended RPM range is 5500/6000 RPM so I’m running about 1000 RPM low. The motor has ~20 hours on it.<br /><br />Loaded weight is 1400/1500 lbs empty (not including me & a passenger or two).<br /><br />I’m running the boat at elevations of 4500 to 6000’<br /><br />Thanks in advance, John

 

[walleyehed]

Re: Need prop size advice

Was the dealer aware of the altitude in which you would be operating this rig????<br />20hrs isn't much time, and I think I would hold off until after 35-40hrs and see if the RPM is still in the same area.

 

[JohnOD]

Re: Need prop size advice

No he was not Kenny. FWIW the dealers shop is located at sea level.<br /><br />Thanks for the sugestion.<br /><br />John

 

[walleyehed]

Re: Need prop size advice

He's most likely over-propped it...takes about 1" less pitch for every 1500ft above sea-level...

 

[JohnOD]

Re: Need prop size advice

Kenny I’ll take your advice & put more hours on the motor before I pull the trigger on a new prop.<br /><br />Theoretically if reducing the pitch buy 1" added ~200 RPM I would need an 11x9 prop to reach 5800 RPM. I see IBOATS (who I plan on buying from) sells 8 & 9 pitch props that will fit my Honda...but they are larger in diameter that what I'm running now. What effect will increasing the diameter from 11" to 12 1/2" have on the motor performance?<br /><br />I will also try some changes in the trim to see if I can boost RPM.<br /><br />I appreciate your help, John

 

[walleyehed]

Re: Need prop size advice

Diameter usually increases with a decrease in pitch..it helps keep the load pushing ability and slip ratio as good as possible.<br />and, due to torque curve< I think I would stay at 10" pitch as the lowest you want.<br />200 per inch kinda goes out the window when below the power band..