Spark Plug fouling on 3hp Merc

[frogman2]

I have a little merc outboard 1989 or 1990 (I am not sure) that I bought used. When I first brought it home I put a new plug in and it started right up. I ran it about 1 hr. and it just quit. I took out the plug and it was all black and oily looking. I replaced it and the motor ran fine...for about 1 hr. and then did the same thing again. <br /><br />I am using 89 octane fuel and merc. premium oil with a 50:1 mix.<br /><br />also I have run it in a garbage can and the water ends up like the plug- all oily ???? Help

 

[12Footer]

Re: Spark Plug fouling on 3hp Merc

The carb is running too rich,or you have the wrong plug in it (too cold). Try turning the idle mixture in a 1/4turn.Wait 3o seconds, then, anotther 1/4turn. Do this until it starts to run rough. Than, back-out 1/4 at-a-time, until it runs rough rich. You can then set the mixture to the midpoint of where it ran smoothest. If you can't smooth it out, or the plug keeps fouling after that, and you are sure it is the proper plug, you may have to pull the carb off and clean it. By the way, can you get gas to leak out of the carb by squeezing the primer?<br />If so, the problem is a stuck float needle.

 

[FlyBoyMark]

Re: Spark Plug fouling on 3hp Merc

Make sure your mixing 50:1 or 16 oz. oil per 6 gal. not 16 oz. oil per gal. if ya know what I mean jelly bean... Seen a lot of guys get brain lock and overlook this.........

 

[Boatist]

Re: Spark Plug fouling on 3hp Merc

Frogman<br />Also make sure motor is warming up. Should be to hot to hold fingers on head for more than about 2 seconds. If it stays cold check thermostat. When motor does not warm up gas does not vaporize so drags oil into piston. When it run normal gas should vaporize but some oil which does not vaporize stays behind to lub bearings.

 

[frogman2]

Re: Spark Plug fouling on 3hp Merc

Where is the thermostat? Can it be replaced if the motor runs cold?

 

[oldboat1]

Re: Spark Plug fouling on 3hp Merc

If you run an engine in a garbage can for an hour, you will heat up the water too much for cooling (motor will overheat), plus the motor's cooling system will be recycling all the exhaust and unburnt fuel that is in the water. It's possible that you have other problems, but I would guess it's long-running in a closed container that is creating the problems you describe.