Yesterday on plane I lost power to the motor and it was sputtering or bogging and I couldn't go above 8mph after that. It will idle fine, run high on RPM's in neutral fine, and today I got on plane actually but if it gets above 4,000 RPM's it starts bogging again and isn't getting enough power or fuel..... What could be the problem? spark plugs? cylinders? fuel line? bad gas? Today going back to the ramp it actually got above 4,000 RPM's and ran fine... I'm stumped.
Motor is a 2 stroke Evinrude Intruder 175 hp

Thanks

Could be a small particle in one of your carb jets...same happened to me.

I would start with plugs first. Then look at fuel system. Ethanol may have deteriated fuel lines as well since the problem seems to be intermittent. Happened to me last summer. Had a fouled plug. Plugs will be the easiest to change and then go from there.

If it just stopped having an issue as sudden as it started and is running fine now, I agree with a particle or blockage in the fuel flow somewhere.

Had the same problem several months back, replaced the plugs and the fuel bulb. Problem solved. Ethanol had eaten up the fuel bulb. Do not replace the bulb with the cheapest one you can find they will not last. Get a Mercury brand or other name brand bulb from your boat dealership. I had already replaced the fuel line. I typically drain the fuel tank every two or three years and clean the tank. That ethanol eats up gaskets in everything it touches and it will leave them in your gas tank. That will clog up the fuel pick up tube and cause a fuel restriction, Also check all of your fuel filters.

I would target the fuel lines first. Had the same issue with mine, changed out lines and bulb from tank to motor and problem solved. Especially when you say it revs fine in Neutral, mine did that as well.

Fuel lines or fuel pump. Sounds like its starving for gas at the higher RPM's. A pump that is failing or on its way out will supply enough fuel for idle, but as soon as you throttle up it immediately starts to bog out.

I have to agree with fitter. Those VRO pumps have check valves that can stick. Only other think I have seen is the anti-syphon valve sticking.

Sounds like fuel, did you possibly look back at the bulb when it was happening? If not and it happens again see if the bulb is sucked flat.

It is not spark plugs. It is Fuel related, when did you last change out ALL of your Fuel Lines and primer bulb? Service the fuel tank {clean it], then you have the carbs to re-build. It is probably dirt or gunk in the seat and needle.

You need to get a compression check on that motor. A Leak down would be better. If you are going to re-build the carbs you might as well switch out the reed valves. Go ahead and check your coils and plug wires. Get rid of that gas.

If you got something in the thermostat and it is not allowing your motor to get up to operating temp. you could foul a plug and that would cause the problem you are describing also.

On an Intruder it is possible, but I wonder if he has checked anything yet.

Just happened to me. I quit using ethanol free gas and that's probably what started it. I would check fuel filters. VRO pump could be the issue too but start with the filters

My boat did exact same thing the ethanol broke down my gas lines and caused me to plug off not letting engine get enough fuel and chocking it down