Rough running Johnson 25Hp

[james thorpe]

Can someone please help, i have a 1997 2 stroke 25hp Johnson it starts ok and everything is fine to start with but after i stop and turn the engine off when i start it again low revs everything is fine but on higher revs it start knocking ive tried changing the plugs and leads even the fuel but the problem still persists, can someone shed some light please

 

[rickdb1boat]

Re: Rough running Johnson 25Hp

Can you reply in a more comprehendeble manner. Hard to tell what you are saying!

 

[ob]

Re: Rough running Johnson 25Hp

jimmmi, Not real clear but I'll take a shot.If your primary problem is stuttering at high speed,insure that your fuel tank is venting properly and the primer bulb is not colapsing when the symptom occurs.If this is not your problem, water check again and when engine starts to hesitate at high rpms try pumping the primer bulb and see if it picks up.If so, may have weak fuel pump , faulty fuel line connectors,or stuck anti syphon valve on tank fitting.

 

[P.V.]

Re: Rough running Johnson 25Hp

Sounds like you are describing the motor going into "SLOW". Is it overheating?? Try this, disconnect the tan wire coming out of the cylinder head. This "temp" switch tells the power pak that you may be getting too hot and reduces the rpms to about 2500 max. If the engine runs up OK with the lead disconnected, you are either getting hot (and the system is working correctly, in which case you must find out why) or the sensor/switch is bad or the pack is tits. Or the leads are shorting to ground.Be more specific on which model you have!!!!