Mark 78A Super Marathon

[Wilsons]

I have been restoring this motor and it runs fine with the water hose hooked up to it, but when in lake barely runs if at all. Any suggestions?

 

[racerone]

?---------What does " restoring " mean here ?------Did you paint the motor to look nice ?---Post more information such as , did you have the pistons out ?--------Did you clean repair carburetors.-------Did you have distributor off ?---------Timing belt on correctly ?---------Does spark jump a gap of 5/16" on all 6 leads ?

 

[merc850]

That's a direct reversing motor it starts "in gear" so you push the throttle forward or reverse while holding the start button and choke. set the lo speed needles 1 and 1/2 turns out. You might have to set the points depending on how many hours have passed.You really need the manual (Mercury 1965 and Prior C-90-25500) for this motor.

 

[Wilsons]

So far I have cleaned and reassembled the carburetors, gone through the complete ignition system and all wiring, replaced impeller, the timing is correct, I have not split the case or had the Pistons out. Compression is good and cylinder walls show no signs of scoring, and I found no signs of corrosion anywhere inside engine. I have done this all refrencing a factory service manual