1979 4 hp only one cylinder firing

[Steve Hengehold]

I have a 1979 4hp Evinrude and only the top cylinder will fire. It will start and run at half throttle but is very rough. Pulling the plug wire on the bottom cylinder has no effect while running. This just started a few minutes into a recent fishing trip. While the motor is running it will intermittently fire on both cylinders in short burst. I have changed the plugs and cleaned the carb and inspected reed valves all appear fine. With the plugs in the plug boot but out of the block top plug appears to have a stronger spark. I have not yet checked compression but the thumb test feels the same in both cylinders. What next?

 

[mikeyzx2]

Re: 1979 4 hp only one cylinder firing

Coil gone bad?

 

[Steve Hengehold]

Re: 1979 4 hp only one cylinder firing

Maybe. If I can swap one side for the other I may be able to determine. That is tomorrow nights project. Thanks for the help.

 

[JB]

Re: 1979 4 hp only one cylinder firing

Replace the condenser and clean and gap the points for the lower cylinder before you start swapping the coils, Henge.<br /><br />You also need to check the centering and clearance of the stator.<br /><br />Let us know what you find.

 

[Chinewalker]

Re: 1979 4 hp only one cylinder firing

Blown head gasket? Any evidence at all of water beads on the plug electrode?<br /><br />- Scott

 

[Steve Hengehold]

Re: 1979 4 hp only one cylinder firing

The plug is clean and dry. In response to JB my plan was to swap the the coil for the top cylinder for the bottom and see if the the bottom cylinder would then fire thereby elimnating the other electrical component possibilites. Is there a problem with my procedure?

 

[chris in va]

Re: 1979 4 hp only one cylinder firing

Didn't they do away with points after '77, or was that just on the 9.9's?<br /><br />Coils don't cost all that much if you determine one is bad. Mine only cost about $35 at the dealer.

 

[Steve Hengehold]

Re: 1979 4 hp only one cylinder firing

This engine does not not have points. I ahve found coils for $22.00 each on line but do not know the availabilty.