Pontoon Prop Question

[bighermHK45]

Pontoon (two tubes): 1997 Misty Harbor 2424CC (24' pontoon)
Weight: 1850 (dry)
Motor: 1999 Mercury ELPTO 115HP
Motor Max RPM: 5250

Ok, I am repowering the pontoon. Going from a 40HP Force (friggin' awesome motor) to the 115 HP Mercury. The 40 HP Force has a 12.1" x 9 pitch prop on it and I maxed out at 18 MPH @ 5400 RPM (with only 2 people on board). So, in researching the 115HP Merc, I am getting mixed reviews on what prop I should use. I have read I should use any prop with a pitch ranging from 11, 13 and 15.

Need some advice on a good overall prop that scoot the pontoon across the water and pull a tube at a decent pace.

Any insight and practical advice would be appreciated.

Thank you.

 

[SkiDad]

I would think the 15 might be a good starting point. If it is too low on the rpm then buy a 13 and keep the 15 for a spare. You would want to shoot for 5000-5300. Is your engine a 4 cylinder or a 6 ?

 

[steelespike]

I couldn't find any Merc 115 pontoon tests But I did find 12 or 15 tests of a competing motors tests.115 hp 2.00 gear ratio.mercs is 2.07
slightly easier to turn.
First thing I always notice with pontoons is speeds are all over the place I just picked 7 tests speeds 23-32 mph props were 11" or 13"
rpm 5600-6000.weights dry 2000 to 2280.
With no indication of tritoons I'm always suspicious of a 115 toon making over 30 mph
Most boats were at least 24' and all used aluminum props.Keeping in mind the gear ratios;
I'm inclined to go with a 11" because if its too light you can still use it by watching the rpm.If your
getting the motor from a dealer they should let you try some props.

 

[racerone]

The 2 + 2 engine may not be ideally suited for continuos slow speed operation.

 

[SkiDad]

I'm not sure I would go 11, but then again I'm not a pontoon user - the main reason I said 15 was b/c of the RPM limit on your engine and also that it's a torquey 2 stroke. Maybe 13 would be a good compromise ? maybe a spitfire prop ?

 

[steelespike]

i have seen 2 ,I believe, independent Spitfire tests with good results.
The pontoon tests I looked up were also torquey 2 strokes.If the 11" turns out too light
he doesn't have to go buy another prop right away if a 12 or 13 turn out too much
He shouldn't run it too much if its lugging.

 

[bighermHK45]

I would think the 15 might be a good starting point. If it is too low on the rpm then buy a 13 and keep the 15 for a spare. You would want to shoot for 5000-5300. Is your engine a 4 cylinder or a 6 ?

It is a 4 cyl. It runs off of 2 cyl for trolling and once it hits 1800 rpm it fires on all 4 cylinders.

 

[bighermHK45]

I really do appreciate all the replies, but I am no closer to making a decision as the replies are very inconsistent on the way forward. Similar to what I have researched. I am looking to buy only one prop as money is a factor. So, I am looking for the best practical option first and then will adjust if necessary.

 

[SkiDad]

Have you tried Mercury prop selector page ?

 

[bighermHK45]

Have you tried Mercury prop selector page ?

They don't have a drop down box for a 1999 so I used a 2000 model when using the prop selector guide. They recommended a 14 or 15 pitch....

 

[jestor68]

My 24 ft tracker Party Barge with a Merc 90 runs a 15 pitch Black Max at 5200 rpm. I suspect that your 115 might do something similar.

 

[bighermHK45]

Got back from the boat dealer today. They said I should be using an 11 pitch prop for my setup... ??? They did not think a 13 would work at all. Not sure what to do now.

 

[SkiDad]

You are wringing your hands too much over a prop. You have had 2 people say 11 and 2 people say 15. Split the difference and get a 13 and get on the water. That dealer is full of crap saying a 13 won't work.