250 SHO want turn more than 5500RPM

[rickbasser]

I have a 2010 Skeeter FX 20 with a 250 SHO motor currently running a FXP 26 pitch prop. The motor was rebuilt at 99 hours and currently has 162 hours. I purchased boat August last yr. At time it had V max 27 pitch prop and top end 74+ with RPM 5900. I switched props to improve hole shot and was running 71mph with 5900rpm. I was running on # 7 on hyd jack plate set on 7. Now for some reason I can't get above 5500 with either prop. Moved up jack plate to 9 still 5500. Moved to 11 still tops at 5500.Dealer thinks I have bad gasoline. I use premium nonethanol gas and use ringfree also have went to three different gas stations. changed 10 micron filter. Lost and flustered

[WPC3]

Possibly power loss from heat and humidity. The increase in humidity seems to bog an outboard down. When the weather cools off and humidity goes down the power will probly come back.

[WPC3]

Another possibly would be to check the air intake on the motor. Make sure a bird or wasp didn't build a nest in the intake.

[hooken203]

Throttle blade opening all the way?

[TOXIC]

Any codes thrown? Compression check?

[rickbasser]

Up at our cabin so don't have tools to check compression will check all ideas on Monday. Thanks for ideas!

[Rich Z]

As with any outboard performance problems the first thing should be addressed is fuel suply and delivery. Fuel filter cleanliness and fuel pressure is critical for optimum performance as is fuel octane level. ECU maybe pulling the timing back if fuel delivery is insufficient to prevent detonation. Also, I have mentioned this a while back that the fuel injectors don't have any filter baskets in them and eventually will lean out causing loss in performance. Air restriction will also reduce performance. Carefully examine the spark plugs. Even coloration of brown paper bag color is what you looking for on porcelain insulator. Any abnormalities in coloration of plugs indicates an issue with fuel or air delivery. Don't try to attempt fixing these issues with changing propellers or adjusting the motor hight. This won't do anything to improve performance when underlying issues are with fuel or air delivery.
Rich

[rickbasser]

Thanks Rich you were right on the mark about prop and height not improving performance, that what was confusing to me. I would change prop to 27 pitch nothing would change. I would raise motor which should cause higher RPM but it didn't. Ive purchased gas at three different service stations with no change. I can check plugs myself but think its time to call dealer again. Rich. thanks again for given me direction to look so I can resolve this issue

[rickbasser]

Thanks Rich you were right on the mark about prop and height not improving performance, that what was confusing to me. I would change prop to 27 pitch nothing would change. I would raise motor which should cause higher RPM but it didn't. Ive purchased gas at three different service stations with no change. I can check plugs myself but think its time to call dealer again. Rich. thanks again for given me direction to look so I can resolve this issue, just set up appointment with dealer Tues morning. Will provide solution found

[rickbasser]

It turns out the FXP26 wasen't best prop for my boat. At dealer, salesman put his Vmax sho 25 pitch prop on. I went to nerby lake and it was a differance of night & day. I had fast hole shot and because of wind I stopped getting on it when I was turning 5800 and speed of 72 water pressure was near 20. So I our purchased a new prop and should be good to go. Ask dealer why raising ht. on jack plate didn't increase RPM. He said they found they don't hold the water like they should. All I can say is V max sho prop made big change. Thanks for all your help!

[Tony Hamilton]

Not to steal or change is thread but is it possible to lose 10 mph with the heat and humidity Day from April to May?? TIA

[Mullins057]

Ive lost 4 to 5 mph from spring to summer heat and humidity.

[jpt7779]

Not to steal or change is thread but is it possible to lose 10 mph with the heat and humidity Day from April to May?? TIA

Plug in your weather numbers and altitude in this calculator. You will find high density altitude, high temps, high humidity, low barometric pressure all kill horsepower (hot humid summer day). Conversely, low density altitude, colder temps, high barometric pressure, low humidity, all increase performance (cold winter day). Doesn’t matter if it is a bass boat, jet ski, car, truck, or an airplane this all effects engine performance.

Simply plug in some numbers, only change one at a time, and see the effect.

https://wahiduddin.net/calc/calc_hp.htm