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1978 mercury 85 hp

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when I run the motor at full

when I run the motor at full throttle the motor will open up for a couple of seconds then die out. I allready checked the dual carbs they are both clean.
 
" I'd be looking into the

" I'd be looking into the way the fuel is delivered to the carbs next. My .02, look at the fuel pump first - but, I'm assuming what you are describing is that the engine gets up to a high RPM and then dies out. If the engine was hesitating or dieing out before it hit a high RPM, that's probably something different.

Disconnect the fuel line where the carbs are fed; squeeze the primer bulb, be sure you are having no trouble getting good flow through, there should be no resistance. Next, pull the MOB switch to be sure the plugs won't fire and kick the engine over, you should have a steady pulse of fuel exiting the line. Tell us what you find.

Jon "
 
" If you happen to have a pres

" If you happen to have a pressure and vaccuum gauge you can test the fuel system. The gauges simply tie into your lines via "T" fittings. On the output side of your fuel pump you should have 3-7 psi. Intake side should have no more than 2" of vaccuum at wide open throttle. Other problems can be air leaks inside the float bowl from old or worn gaskets. This will prevent emulsification air from being able to lighten the fuel enough to travel up the main tube. Also, if the float drop isn't set right the needle may not come away from the seat far enough to allow the needed amount of fuel to enter the bowl.
Good Luck "
 
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