Fouling Plugs

solasylum · #1 03-19-2002, 11:35 AM

I need some help! I have a 1992 25 hp Evinrude motor that I continually have a problem fouling out the spark plugs. The lower spark plug is the one that generally seems to have the problem. Is this possibly from not shaking the gas & oil together once I have added some gas/oil? I do shake the gas can but perhaps I am not shaking it enough? I just bought new plugs and ran the motor one day and it ran fine. I add some gas/oil and shake to can to mix them together. I get to the launch and use the primer ball to gas up the carburetor. I start the boat and it run's fine for a second and then the motor acts up. I take out the lower plug and sure as hell it is wetter than an umbrella in a rainstrom.

Any ideas? Can I run a hotter/different plug to prevent this from happening? Right now I am running the recommended plug from Champion.

Thanks,

Scott

***ESOX*** · #2 03-19-2002, 11:42 AM

Cheap fix, replace the coil for that cylinder, about 20 bucks.

solasylum · #3 03-19-2002, 12:34 PM

Esox...you'll have to excuse my ignorance because I am not a mechanic. Is this because the existing coil isn't allowing a hot enough spark? This then causing the oil to accumulate on the plug? Can I switch the coils around to see if in fact this is the problem? You don't think this would be caused by inadequate mixing of the gas/oil together?

Thanks for your help and quick reply!!

***ESOX*** · #4 03-19-2002, 12:49 PM

Yep, a weak coil will spark erratically, and the plug will foul because of the accumulation of unburned oil on it from the missed sparks. mid 80's - mid 90's OMC's are notorious for needing coils fairly regularly. You could switch the coils around , a simpler test would be to take them both off and have them tested at the parts store.
PS always add the oil to the can BEFORE adding the gas.

**STEINFISHSKI** · #5 03-19-2002, 01:22 PM

I have 2 suggestions I learned both the hard way.

First with the main tank and my 2 stroke motor I would pour most of the oil, gas, and then top off with oil. If I did this just before going out I would fire up the motor and when it got just about warmed up it would sputter and die. Gas line was too rich to burn. I had to disconnect the gas line just before the floats and squeeze the bulb to flush the rich mixture until it more resembled gas which would burn. I then would pour the mix back into the tank for proper mix ratio, prime and restart the motor. I think I did these steps 3 times before I started filling up with gas after fishing so I never had to mix just before starting the motor.

Second always use a premium oil. A company can mix TC3W in dog ***** and meet manufacturers requirements, but it will foul your plugs even after a short time, especially at trolling speeds. Replace the plugs, and use only Quicksilver, Evinrude, or other premium oil mix and see if that helps.

grizzly · #6 03-20-2002, 03:31 PM

Just went threw the same senario with an older 15hp johnson. Esox is right on with swapping the coils, we discovered it buy running the motor at night. There was spark jumping to the block right out of the side of the coil. You could try firing it up with the cover off at home running it with the muffs in the dark. The light show is pretty cool, not to mention watching my buddy get zapped really good also. He will never touch a motor again running. We replaced that coil and it ran good for 2 outings, then the other coil went out too.

Grizzly

solasylum · #7 03-21-2002, 01:26 PM

Esox...thanks for the posts! Would a normal marine parts store be able to test the coils for me? Could they be tested at an auto parts store? Also, how do I add the oil before the gas if I don't know how much gas it takes to top off the tank? Could I do like stein suggested and add some oil and the after I top off the gas add the minimal amount of oil to make the ratio correct?

Thanks for all your help as we probably all know how it sucks to have motor problmes when you are trying to hook fish!!

Scott

Mike · #8 03-21-2002, 02:06 PM

solasylum,

You might want to consider buying a plastic gas can (about $10). Mix and store your gas/oil in it, then fill your gas tank from that.

Mike

**WALLEYE MIKE** · #9 03-21-2002, 02:16 PM

Solasylum, I had a bad coil on a 3-wheeler. I got the specs for it and checked it out myself with a volt meter. If I remember correctly had something to do with ohms. Resistance was involved. Oh yeh, found the specs in a repair manual I had bought.Cost me (the manual) the same as if they had to check it out. This manual showed where to connect the leads.

***ESOX*** · #10 03-21-2002, 02:23 PM

solasylum, Most parts dealers are capable of testing coils, just call ahead of time to make sure. Oftentimes a visual inspection is all that is neccessary to confirm a bad coil, if the case or the potting is cracked, replace the coil. (The potting is the sealant on the back side of the coil.)

solasylum · #11 03-21-2002, 04:27 PM

Wow.....what a bunch of great suggestios!! I like the idea of putting the gas/oil in another can and then using that to fill off my gas tank! ESOX...I will be looking over my coils for cracks and wear! Walleye Mike....I have the motor manual and an electrician friend and I'll see if he can check them out if I can't find a parts place to do it for free.

Thanks a bunch guys!! I sure am glad I can come to a place like this and get this kind of help!

As I said before and will say again.......I am proud to be a Michigan Sportsman!!

Scott

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