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1986 50hp merc 0A987251

R

rlawton

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I have a 50hp merc serrial # 0A987251 1986? 3 cyl that has just been rebuilt and will not fire on the bottom cylinder compresson is good and has spark although i am not sure if its fireing at the right time (bad trigger) or the guy who did it put the reed valves in incorrectly it has new everything reed vavle boysen 2 stage,bored .30 over ,rebuilt carbs,new switch box,stator,coils,plugs an wires,new seals and gaskets everywhere i realy need help with this one i have alot of money in this motor and it wont run the mech working on it has thirty years exp and cant figure it out and i have lost confidence in his ablility :confused:
 
Since the motor has just been rebuilt, and if you are seeing spark at the 3rd cylinder, then it must be a fuel problem.

The timing will not be off for a single cylinder - the trigger either works or doesn't work - it can't fire "at the wrong time" for cylinder 3 if cylinder 1 and 2 are firing at the "right" time - just not possible.
 
Was the crank replaced in this engine? Are you checking spark with the plug installed or without. What is the compression on #3. The reeds are pretty hard to install incorrectly on that motor. Do you have the part Number on the Boyesen reeds you used.

Tell me the wiring colors on the switch box from top to bottom vertically and then the wiring colors from left to right horizontally.
 
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i am not sure what the wiring is he said he has tried four diffarant possable combos on the switch wiresand still nothing the motor had the same problem before it was rebuilt and the carbs have been went thru sseverl times does any body know for sure what the correct wiring is for this motor
 
when you spin it over does the bottom cyl go poof, if no poof then its not holding its fuel charge and mostlikely the lower crank seal
 
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