Another pontoon prop question

mla2ofus

Chief Petty Officer
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Dec 30, 2008
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571
24' Landau 2 tube w/ 90HP Force. Has 14 x13P prop. Motor ID tag says 5250RPM max. It will go to 6000RPM at WOT. Will I gain anything w/ a prop w/ more bite? It works great for trolling as is and will do about 20MPH at 5000RPM. Just curious.
TIA,
Mike
 

steelespike

Supreme Mariner
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Apr 26, 2002
Messages
19,069
What year is the motor? I think if it is making 6000 rpm it is either a bad tach or it is ventilating.What is the speed at 6000?
 

mla2ofus

Chief Petty Officer
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Dec 30, 2008
Messages
571
Motor is a '98, it does about 22MPH at 6k. Tach shows idle speed of 1k. I never run it over 5k since that's what the motor tag says.
Mike
 
Last edited:

Sea Rider

Supreme Mariner
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Sep 20, 2008
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12,345
Probably engine is propped wrong ? If tach is ok, engine well height seated and 90? trimmed, need to gor for at least +1 pitch size (14) to lower wot revs down to near 5250 wot rpm factory range.

Happy Boating
 

steelespike

Supreme Mariner
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Apr 26, 2002
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19,069
That uses a Merc leg I believe a 2.30 gear ratio. Prop sizes 11",13" and 15" on typical pontoons.
I still feel that a 90 hp Force isn't likely to make 6000 rpm with a 13" prop on a 24 ft pontoon. also a little unlikely to make only 22 mph at 6000.
But pontoon speeds are all over the place for no obvious reason.Was 22 a gps speed?
I found some recent new 90 hp 2 stroke motor tests with about the same gear ratio 2.36 2, 22 footers with 15" props turned 5500 @ 25 mph,and 5150 @ 23.
2, 24 footers 13" 5400 @25.4, and 11" 5600 @ 23.5 these new 2 strokes rated at the prop highest rpm was an 11" @ 5600. And that with a
​ slightly easier ratio.
 
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