Suzuki 140hp four stroke 2003 electrical problem?

[mhillsydney]

Hi, ive got a 2003 White (Johnson branded) Suzuki 140hp engine on a Haines Signature 600F - its a great rig but im having trouble with the engine working beyond 8-9knots. Even at flat out thats all it gives me sometimes then all of a sudden comes to life and works perfectly?? first i thought it was fuel, then spark but a mechanic suggested it may need a whole new control box and wiring loom - but thats not the diagnosis, its just a thought because the engine still starts all the time and runs perfectly most times but sometimes (becoming more often...) it just chugs beyond that 8 knots or so - its like it is being goverened?? but no alarms and earth is fine also. A mystery??

any thoughts welcome?
thanks

[Moonlighter]

Has the mechanic hooked it up to their laptop and run thru all the diagnostics? That should tell the story, especially if there's a fault in the controls.

If that doesn't show anything, then suggest you check all fuel hose connections, fuel lines for any splits or cracks, and the vapour separator - could be either a air leak, or some dirty fuel causing a blockage somewhere in there. I'd change/check/clean all the fuel filters too just to be safe.

Hope that helps

Cheers

ML

[mhillsydney]

thanks - changed plugs etc and took it out today for a faultless run - a mystery! maybe just a bad plug after all??