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Old 11-20-2006, 11:20 AM
jkenan jkenan is offline
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MMO or Cool temp contributing to fouled plugs

After rebuilding my engine last winter, it ran great all summer, after going out several times this fall and winter, I have had a terrible time with fouled plugs.

The first sign of trouble was mid-October (after not being used since Labor day weekend), when the engine had very little power and sounded like it wanted to stall. I dis-assembled and cleaned the carb, but determined that was not the issue since it was already very clean. I checked my fuel vent, and it was fine. Finally, I removed the plugs to squirt some MMO to valves, which I thought were stuck. After doing that, I inspected the plugs, and they were badly fouled, so I replaced them. Engine ran great. At the end of that trip, I filled up and put high a bit more than the 4oz to 10gal MMO ratio in the gas, and squirted some more MMO in the combustion chamber, both for good measure. A couple of weeks later I used it, and it ran great. Before leaving it, I repeated the same. This past weekend, same problem. I pulled the plugs, and they were badly fouled.

I realize there could be several things going on here:
1) Too much MMO in the gas - exhaust smoke is white, but seems to dissipate into the air very quickly. This makes me think it is just vapor from the cooling water interacting with the cold air, and not oil - either MMO or oil getting past the rings (oil level remains steady).

2) Too much MMO squirted into the combustion chamber - could this foul plugs quickly? The first time I had a loss of power issue, it could very well have been stuck valves which was resolved by MMO.

3) Engine running too cool - average running temp is about 130 degrees. During the summer when the water was warmer, it was about 140 degrees. How can you make the A4 run hotter besides partially closing the seacock - which I did this last time out, with new plugs (I did not squirt any more MMO into the chamber after replacing the plugs) and they seem pretty clean after motoring about 6 hours?

I know I probably need to approach this more methodically, but as the problems surfaced, I did what I thought was necessary to get it running again, without proper thought to testing the cause. I won't be using the boat for the next couple of months, so I figure would be best put this all out to the discussion board for feedback.

Thanks for any thoughts on the matter.

John Kenan
Ericson 29, Carried Away
Efland, NC
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Old 11-20-2006, 09:19 PM
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MikeB.330 MikeB.330 is offline
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Are the plugs you are using the correct heat range? I believe that Don has some listed that run a little hotter than the Champion J12 plugs.

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Old 11-21-2006, 07:34 AM
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jhwelch jhwelch is offline
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I had a bad case once of fouled plugs when my choke stayed closed
even after I had pushed in the handle to the open position after
starting the motor. It should be pretty easy to take the air filter/
backflame arrestor off and look inside the carb. throat to make sure
your control cable is operating properly.

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