More MPH out of my 2250GL

Commdiver77

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New owner, never had a pontoon or outboard, owned a couple mastercrafts and props and pitch were not a worry. My current set up that I bought it used with is a 90hp Yamaha 2 stroke with a 13.5 x 16 on it. GPS tops speed 18mph and max rpm at wot 3400. I know this motor should run wot around 5500-6000 according to what I have read. My question what diameter and pitch would give me around 20-23 mph and 5500-6000 rpm?
 
Assuming your tach is correct (I would check it against a shop tach) the motor is lugging badly at only 3400 and will lead to premature failure running in this condition. 2 strokes do not like lugging and cylinders overheat quickly causing compression loss and then overhaul. If you have the Yamaha tach it can be adjusted on the rear on the gauge.

To answer your original question, I would borrow a 12 pitch prop and test run it in the water from there changing pitch until your engine is around 5800 - 6000 rpm at wot with boat loaded on the light side. Many dealers and prop shops will allow testing before buying. As far as top speed you take what you get after rpm is correct. Be sure the outboard has a good solid tune up and running good before testing.

FYI - your Yamaha has a rev limiter that comes on at 6100 so if you see that rpm while boating you may be able to swing a higher pitch prop. Better to pull rpm down with load than run against rev limiter all day.

I have a 115 Yamaha 4 stroke on my 22SSRX Bennington and it does 30mph GPS at 5900. Remember mine has 25 more hp and is 4 stroke engine. I do this with a 14 by 12 pitch prop that came as 13 pitch but I had it bent down a degree. I think you could be close with a 13-13.5 by 12 pitch on your boat and a good place to start.

Good Luck and please post your results for others to see and use.
 
Try some where a 13.5 X 11pitch or a 12pitch Your 16pitch is way off for sure .Just be sure your Tack is working correctly first, I think the tack is wrong also since you are seeing 18 mph at only 3400 rpms, that does not seem correct to me. too much speed for that low of rpms I have a 2250gl 2 toon, with a 115 yamaha 4 stroke and have two props the 15P gives me 27 mph at 5600 and the 13p gives me 29 mph at 5900 these are alu. props
 
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