1987 Johnson 15

[beardsy]

Hi I have a 1987 Johnson 15 horse motor, it has been tuned up and ran for a very short time. I just started it up today, it starts but will not keep running, I'm assuming the carb is jelled up or it is old gas causing the problem. I also noticed a gray residue coming from the center of the prop, is this normal? It is a two stroke engine. Help!

[oldcatamount]

I had the exact motor ('till I sold it last month). The plugs should be gapped at .040. Gapping at .030 will cause the grey residue you mentioned (un-burned fuel). Fresh fuel is a must (50:1). Cleaning the carb is yearly maintenance as far as I'm concerned. If you don't use the motor much, the carb will need cleaning more often. Sweet motor, kick myself for letting mine go.

[Daviet]

If the compression and spark are ok, you will probably need to overhaul the carb.

[beardsy]

I had the exact motor ('till I sold it last month). The plugs should be gapped at .040. Gapping at .030 will cause the grey residue you mentioned (un-burned fuel). Fresh fuel is a must (50:1). Cleaning the carb is yearly maintenance as far as I'm concerned. If you don't use the motor much, the carb will need cleaning more often. Sweet motor, kick myself for letting mine go.

Thanks very much for the information, I was not aware of the .040 gap setting, i'm sure it will make a difference.

[beardsy]

thanks for taking the time to respond! I will overhaul the carb.

[beardsy]

I had the exact motor ('till I sold it last month). The plugs should be gapped at .040. Gapping at .030 will cause the grey residue you mentioned (un-burned fuel). Fresh fuel is a must (50:1). Cleaning the carb is yearly maintenance as far as I'm concerned. If you don't use the motor much, the carb will need cleaning more often. Sweet motor, kick myself for letting mine go.

How should I adjust the fuel mixture knob? I turned it in all the way and backed it 1 1/4 turns, will that work?

[Daviet]

If your carburetor has a plastic top, some of those used a static setting of 2 1/4 turns out from lightly seated. Metal carburetor is 1 1/4 turn out.