4 blade Spitfire prop for Pontoon?

[bighermHK45]

I noticed that during my testing of the the motor height of the Merc 115 2 stroke on my 24' pontoon, I have very weak water "bite" in reverse and steering at low speed is sketchy at best (not that it is supposed to maneuver like a sports car). But it is noticeable and since my wife loads the pontoon for me since she refuses to back the trailer down the boat ramp, I need to make it as controllable as possible.

So, I have read a 4 blade Mercury Spitfire pontoon specific prop will help with what I am after. Currently, I have a 3 blade Quicksilver Black Max 11 pitch on it now and it seems to perform decent overall. I don't want to lose too much top end if I do switch to a 4 blade.

And lastly, if I do switch to a 4 blade, do I keep the same pitch as the 3 blade or go up to a 13 pitch. The Mercury website prop selector indicates I would gain about 4 mph at top end if I use the 13 pitch. It doesn't make sense to me, but maybe someone can explain the characteristics better to me.

Thoughts?

 

[HotTommy]

I don't know the answer. If you don't get a satisfactory answer here, you might want to repeat your question on the Propeller specific forum.

 

[steelespike]

Typically it is suggested to decrease pitch 1" going to a 4 blade.I do believe it is usually suggested to use the same pitch with the Spitfire.
Increasing pitch seems unusual but depends some on your present numbers.
4 blades typically improve hole shot, stay on plane easier at reduced throttle,seem smoother and respond better around the dock.
Spitfire is said to maintain top speed but I haven't seem any pontoon numbers.
It seems to me a 4 mph increase is a tough assignment with a pontoon.

 

[Jeep Man]

Typically it is suggested to decrease pitch 1" going to a 4 blade.I do believe it is usually suggested to use the same pitch with the Spitfire.
Increasing pitch seems unusual but depends some on your present numbers.
4 blades typically improve hole shot, stay on plane easier at reduced throttle,seem smoother and respond better around the dock.
Spitfire is said to maintain top speed but I haven't seem any pontoon numbers.
It seems to me a 4 mph increase is a tough assignment with a pontoon.

What he said. When I switched to a 4 blade, I dropped the pitch by 1. Speed did NOT change and RPM stayed the same. Hole shot and reverse control was a little better.

 

[bighermHK45]

Today, the best WOT was 23 MPH (GPS) at a range of 4900-5400 RPM. The cross/head wind (17-20 MPH) and chop on the water was not ideal conditions for testing. Not sure if this '99 Mercury 115 has a rev limiter or not but when it hit the 5300 - 5400 RPM the motor dogged out and I had to throttle back. Based on the conditions today the WOT averaged 22.5 MPH at 4900-5200 RPM.

So, based on these results, I am guessing I could go to a 13 pitch 3 blade as there seems to be more MPH to be had as the 11 pitch seems to be increasing the RPM before I can get to the maximum MPH?

Or should I go with a 4 blade 11 pitch, which (if I understand correctly) will drop my RPM slightly and put me in the 5250 RPM the manual calls for at WOT?

Thoughts?

 

[Bamaman1]

Pontoon boats are displacement hulls, and they have their speed limitations. They'll get up to about 25 mph, and it's like hitting a wall. To get any more speed out of the hull, you've got to have lifting strakes on the hull to get the nosecones out of the water or much more horsepower.

I suggest you go with one of the new model of propellers specifically designed for pontoon boats in a 13 pitch. Mercury and Yamaha both have such propellers. 4 blade props are really seldom seen on pontoons.

I'm running a Yamaha Reliance 15 pitch prop on a 24' Bennington with a F150 Yamaha 4 stroke. I'm seeing 6000 rpm's at 40 mph--just perfect.

 

[bighermHK45]

Pontoon boats are displacement hulls, and they have their speed limitations. They'll get up to about 25 mph, and it's like hitting a wall. To get any more speed out of the hull, you've got to have lifting strakes on the hull to get the nosecones out of the water or much more horsepower.

I suggest you go with one of the new model of propellers specifically designed for pontoon boats in a 13 pitch. Mercury and Yamaha both have such propellers. 4 blade props are really seldom seen on pontoons.

I'm running a Yamaha Reliance 15 pitch prop on a 24' Bennington with a F150 Yamaha 4 stroke. I'm seeing 6000 rpm's at 40 mph--just perfect.

Well, I tried the 4 blade 11 pitch and it did not perform as I had hoped. It definitely had great hole shot but it was a dog at top end. I lost 2-3 MPH and it would only max out at 4900-5000 RPM. Pretty lame. So, back to the drawing board I guess... Not sure a 13 pitch would help my cause or not.