early 1960's 40 hp spark plug issue

[Woodstock60]

The lower cylinder started cutting out on this motor, so the first thing I checked was the plugs and the lower was loaded with wet gooey carbon. I cleaned both plugs and reinstalled and ran for a few hours, she started to run rough again so I pulled the plugs and the lower was starting to load up with the wet carbon again. Does anyone know of a common cause for this, could it be a week coil or a bad wire or plug, just looking for input before I start replacing every thing. Thanks

 

[Tim Frank]

Verify spark quality....check compression....if both OK, it's a fuel problem.

Before you "start replacing everything", depend a few $$ on an OEM manual.
It has good T/S sequences specific to your motor that will save you many times the manual's cost.

 

[HighTrim]

I would inspect the spark quality first. Get an inline tester for this, may simply be points need cleaning.

Maybe crankcase drain plugged? Rich mix?

 

[Woodstock60]

Thank you guys, that's what I thought it would be, am currently changing points, and while I'm in there I have a spare coil, I did already check the compression as this is a frankenstein restoration project. The points on that cylinder do look worn, don't know how I missed that one because I put the armature plate together. Will test and report

 

[F_R]

"1960's" isn't specific enough. If it is early 1960's, with a fuel pump on one side, with a hose running around the rear to the lower bypass cover on the other side, the fuel pump diaphragm may have a hole in it. That will feed extra gas through the hose to the bottom cylinder, causing rich running and plug fouling.

Test: Remove the hose and squeeze the primer bulb. If gas leaks out of fuel pump, diaphragm is shot. New ones are available here at iboats.

 

[Woodstock60]

It does have the old style glass bowl fuel pump on it which I thoroughly cleaned and installed and although I tested to see if it pumped I did not test for that. Will check tomorrow. Thank you. That little bit of info is the exact reason I posted this question. I wouldn't have learned that anywhere else.

 

[Robert Ellis]

I run a 63 40hp evinrude regularly. Don't know what plugs you use but I find the J6C plugs stay noticeably cleaner than the J4Cs. I also don't use the original 24:1 mix ratio ... 40:1 seems to work fine ... been using it for years with no troubles. Sounds like your troubles may be more severe than what I'm suggesting but when you get it sorted, try the above (particularly the plugs).

 

[Woodstock60]

Ok, so I think the problem was two fold. first, the points were crap and anything less than brand new points does not seem to work for me. Second, and it took me a while to notice this, is the spring in the boot of the end of the plug wire was all rusted. I think from now on its new wires, boots and springs on every rebuild. Thanks for all the input. By the way the plugs were j6 and I use a 50/1 ratio.

 

[Robert Ellis]

Nice one! Enjoy that motor - I wouldn't trade mine for anything. Maybe I should try a 50:1 mix - I thought maybe I was pushing my luck at 40:1!