tohatsu mystery?? tried everything

[verg]

I have a 2000, 70 hp Tohatsu that recently started acting up. I have had it in the shop a few times and they cant seem to figure out the problem. the engine runs great below 3200 rpm, but if I try to throttle up beyond that, it starts to shudder and bog down. they cleaned the carbs, replaced the plugs twice, and the resistor caps, but still no good. the engine will be ok for 20 minutes or so when I first take the boat out, but then the problem returns and gets progressively worse the longer it runs. Any ideas? I will have to take the mechanic out on the boat because it doesnt run bad in the shop, only under load. thanks David

 

[Fouled Plug]

Re: tohatsu mystery?? tried everything

Have they tested the stator yet? Sounds like it may be related.

 

[salty_dawg2]

Re: tohatsu mystery?? tried everything

Do you have a water separator filter? If you do, and the filter is all gunked up, you could get a good flow of fuel at idle or low RPM until the gunk was sucked against the "out" side of the filter, then things would start bogging down.

 

[verg]

Re: tohatsu mystery?? tried everything

Thanks for your help. I am going out tomorow with the mechanic from Tohatsu shop to see if he can figure it out. Any ideas on what he should try? new tank and gas line? someone told me to engage the choke while the engine was bogging down, if it runs better-its a fuel/carb problem. if it runs worse, its electrical. dont know if this is true or why. I'm ready to try anything, this has been going on since june!