won't go fast

[tomsteelie]

Just picked up a merc 70 h.p. thunderbolt, heard their decent motors. Well previous owner stated started fine but had no kick. Took it out and runs smooth but only about 10 mph. When I held the choke button in motor speed up to about 20 mph smoothly. Should I change fuel tank, check fuel filter, When I gave it full throttle seemed to back down? can anyone help, always had a johnson.

 

[Plainsman]

Re: won't go fast

Welcome to iboats!

I'd start with checking compression, spark and fuel. Does pumping the fuel bulb help?

 

[tashasdaddy]

Re: won't go fast

agree, what year, and serial #. also dirty carbs.

 

[studlymandingo]

Re: won't go fast

Holding in the choke button should've loaded it up and killed it while you were running. Sounds like fuel delivery to me too, gummy carbs or the like.​