Tohatsu 9.9hp 1986 M9.9B = losing power at the top end

[squidhunter]

Hi All

I have recently purchased a Tohatsu M9.9B. I took it for her first run and it started first shot every time, probably is as you reach full speed it loses power. If you return to half throttle it is ok but WOT it loses power every time. I know it has been sitting around for a while.
Any Suggestions would be appreciated.

 

[pvanv]

Re: Tohatsu 9.9hp 1986 M9.9B = losing power at the top end

Be advised: The 9.9B is long obsolete.

No carbs are available, though a few internal carb bits may be had, depending on which carb you have.

The good news: Water pump kits are still available for the foreseeable future.

If you want to wrench on this motor (or any motor for that matter), I would recommend you start with the Factory service manual (not an aftermarket manual), available from any dealer (including me.) Then diagnose the fuel, electrical, and mechanical systems.

Your symptom could be almost anything, but is likely either fuel starvation, out-of-sync ignition, or possibly a bad head gasket.

 

[squidhunter]

Re: Tohatsu 9.9hp 1986 M9.9B = losing power at the top end

thanks got some carby spray onto it and it did the trick

 

[pvanv]

Re: Tohatsu 9.9hp 1986 M9.9B = losing power at the top end

thanks got some carby spray onto it and it did the trick

Doubtful. Spraying solvent down the carb throat only makes the carb shiny, and does nothing for the internal fuel passages. More likely is that running the motor has helped dislodge/dissolve some varnishing accumulations in the power circuit.