50 HP Honda limited RPM

Ive got a 2010 50 hp honda fuel injected and she wont rev out , ive tried with no load and with load and she struggles to get over 3500 rpm . Ive checked the fuel lines and filters , disconnected the throttle linkage and tried reving it by the throttle body . Could it be the TPS sensor ? There are no alarms

Could it be the TPS? Maybe, but normally it would throw some sort of code. You would have to change the entire throttle body to replace it...$284

First thing to do is do a compression check.

I am assuming that it ran ok before this with the existing prop...if not....it could have too large pitch of a prop.

Have you checked the high pressure filter in the vapor separator? Have you drained the vapor separator to see what the fuel looks like?..you could just have bad fuel.

You might have an air vent blocked...like the vent for your vapor separator or a crankcase vent.

Generally, you should not be able to rev it above 3500 or so in neutral because the ECM is limiting it since it is not in gear.
That being said, check to be sure that your neutral safety switch is working properly. If the ECM thinks you are in neutral, even if you are in gear, you will do exactly what it is doing for you. In neutral, the switch should have continuity. In gear, it should be open.

You did not say how smoothly it was idling. You can check to see if all cylinders are firing by removing the spark plug wires one at a time (with insulated pliers) while the engine is running. The engine should reduce in speed with each plug wire removed. If you remove one and it does not change the motor, that is the troubled cylinder.

There are a few alternatives.

Mike