1969 Evinrude fouling middle plug

[bryanflood]

I have a 1969 Evinrude 55 horse. It runs great but after about 30 minutes of running at higher speed the middle spark plug fouls. The other two spark plugs look great. Does anyone know what I should check? I cleaned out the carbs? What could be causing one plug to foul and not the others?

Bryan

 

[James R]

Re: 1969 Evinrude fouling middle plug

You say you cleaned out the carbs. The question arises was it done correctly with new kits fitted and the float heights set correctly. That carb could be flooding.
Have you checked the compressions. If the compression is low on that cylinder the fuel will not burn and oiling will ensue. Are the plugs of the correct type and new. A plug failure can also produce your symptoms.

 

[bryanflood]

Re: 1969 Evinrude fouling middle plug

Thanks for the tips, I checked compression and found 130, 145 and 135 with the 145 on the middle cyclinder. So the fouling doesn't seem to be compression related as the plug that is fouling is in the cylinder with the best compression. I will check the float height this weekend. Hopefully that will be the solution. Does anyone know the correct float height, I don't have a manual here anymore (checked it out from the library)?

Thanks,

Bryan

 

[Bumpa53]

Re: 1969 Evinrude fouling middle plug

Hi Bryan,

On a 1970 60 HP with similar configuration the float "height" is checked by disassemblng the carb and turning it upside down so the float rests on the needle valve. In this position the requirement is for the float to be parallel to (and above) the carb flange. The float arm should be adjusted (bent) to achieve the parallel alignment. Do not apply pressure on the needle valve when making an adjustment.

There is also a "Drop" adjustment from the flange to the top of the float with the carb upright but I don't have my manual handy for the measurement. I could get that number over the week-end.

B53

 

[bryanflood]

Re: 1969 Evinrude fouling middle plug

Hi,

B53 thanks for the info, my middle carb float appears to be about 1/16 or so too high, so I adjusted it down a bit similar to the other two carbs and they are now all parrallel to the float bowl mounting flange.

I'm a little puzzled about the drop height adjustment. Could you give me a bit more info on this? What does this drop adjustment set? does it just keep the float from sticking in the bottom of the bowl?

I'll probably go out tomorrow for a test run.

Thanks,

Bryan

 

[jasper60103]

Re: 1969 Evinrude fouling middle plug

I don't have the measurement for your carb, but the drop adjustment is shown in the lower picture in the attachment.