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?

 

[Sea Rider]

Some issues :

-Most props are pigs when reversing.
-Pontton boats are not that neat to maneuver compared to a traditional hard hull boat.
-Your wot rpm is needed to check if pontoon is inside safe wot numbers for that engine with current prop.
-Your GPS speed is needed to compare to other prop if going for other one.
-From there can go selecting a different prop to suit you boating needs.
-If going for a 4 blade prop must go one pitch down.

Happy Boating

 

[bighermHK45]

Some issues :

-Most props are pigs when reversing.
-Pontton boats are not that neat to maneuver compared to a traditional hard hull boat.
-Your wot rpm is needed to check if pontoon is inside safe wot numbers for that engine with current prop.
-Your GPS spped is needed to compare to other prop if going for other one.
-From there can go selecting a different prop to suit you boating needs.
-If going for a 4 blade prop must go one pitch down.

Happy Boating

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?

 

[Sea Rider]

Before venturing going for any other prop, you should test combo on flat glass no wind water cond. Testing on other than non ideal water conditions will achieve different performance results than wanted.. With spot on wot revs can go from there selecting pitch or less, more prop blades.

Happy Boating

 

[bighermHK45]

Before venturing going for any other prop, you should test combo on flat glass no wind water cond....

That may be tough to come by... we have wind on a daily basis where I live. Hopefully I can catch a quiet day on the water soon as I need to get this figured out as soon as possible.

 

[steelespike]

I doubt it has a rev limiter and it isn't likely it would cut in at 5300.
If you boat in mostly rough and windy conditions a 11" 4 blade should help
keep the bite and should help control around the dock.
Also the v4 blades may limit the rpm spikes.
Isn't it less wind in the early morning or evening?Perhaps in the lea of an off shore wind
perhaps the lea of an island or a sea wall.Drive into the quiet area at speed.

 

[bighermHK45]

I doubt it has a rev limiter and it isn't likely it would cut in at 5300.
If you boat in mostly rough and windy conditions a 11" 4 blade should help
keep the bite and should help control around the dock.
Also the v4 blades may limit the rpm spikes.
Isn't it less wind in the early morning or evening?Perhaps in the lea of an off shore wind
perhaps the lea of an island or a sea wall.Drive into the quiet area at speed.

Mercury customer support indicated the outboard has a rev limiter. I will try and get out early in the morning and hopefully take advantage of some calm water.