1978 Mercury 90hP power problem

[KimP]

Hello,

Does anyone have any suggestions on how to trouble shoot a power problem that involves the number 3 and 4 cyclnder spark plugs being dry and 1,2,5,6 are working fine. The motor is slow out of the hole and seems to be running half power like it is dragging. Every once in awhile it will get a burst of energy but will stop after a 1 minute or so. There seems to be fuel to the carbs but nothing to the two of the six cylinders. I am open for any feedback and suggestions. Thanks in advance.

 

[Chris1956]

Re: 1978 Mercury 90hP power problem

Cylinders 3 and 4 are fed by the middle carb. I would be looking at it for air leaks and fuel passage clogs.

Also check the compression. Cylinder 3 is most succeptable to damage from running lean or overheating.

 

[turbinedoctor]

Re: 1978 Mercury 90hP power problem

You say you seem to be getting fuel to all the carbs but is it getting into the middle carb bowl. Pull the top of the carb and see if there is any fuel in it. If not it could be the needle valve is stuck closed.