Fouling plugs on Merc 280

[Rule for you]

I'm using the correct plugs and have had the fuel ratio set at -1 by my Mercury dealer. After running several hours and then stopping the plugs will be extremely oil fouled, and the engine won't crank. I will have to clean the plugs to get home. My injectors have been cleaned with low hours on them. Has anyone had this problem? Thanks

 

[gmorgan]

I have been told that if you allow the ecu on a 280 motor to see a voltage below 12 volts it can reset itself to a rich setting until it is exposed to 12 plus volts again. Darrell Pettefer is supposed to be a 2&0 guru.

 

[Rule for you]

My Mercury mechanic thought that , last year and replace the battery. He said all the vital be signs are good. Compression , fuel pressure, fire, etc. He set the fuel ratio to -1, but fouling is still ocurring. This problem has been constant for the last 30 hrs of run time. I have tried 4 sets of plugs, 2 sets of fuel injectors. I have not tried replacing the coils. Should I do that. My worst mistake was to get rid of my 1997 Promax 225, I put close to 400 hrs on that motor with no issues. I carry a paddle with this motor or ride close to the bank so I can change plugs. No more planed river trips untill I find the problem. Ok thanks for letting me vent!

 

[dubmoney]

I don't own a 280, but on the 260, the air temp sensor, can start giving abnormal signal to the computer. I would make sure your mechanic has tested the air temp sensor, it should give certain values for different temps. Also engine temp sensor. Sounds like the computer isn't coming out of cold start. Do all the plugs look the same? What controls the fuel pressure on a 280? To much fuel pressure, could be a problem.

 

[brund]

Is your butterfly on the horn set to 0.0005 to 0.0006 at idle ,also I use the h8 plug instead of the H9 it runs hotter

 

[brund]

Also when you're idling have your motor trimmed up some that also helps

 

[Rule for you]

I don't own a 280, but on the 260, the air temp sensor, can start giving abnormal signal to the computer. I would make sure your mechanic has tested the air temp sensor, it should give certain values for different temps. Also engine temp sensor. Sounds like the computer isn't coming out of cold start. Do all the plugs look the same? What controls the fuel pressure on a 280? To much fuel pressure, could be a problem.

 

[Rule for you]

Thanks for the reply Dobmoney, I will get him to check all of the issues you mentioned.

I don't own a 280, but on the 260, the air temp sensor, can start giving abnormal signal to the computer. I would make sure your mechanic has tested the air temp sensor, it should give certain values for different temps. Also engine temp sensor. Sounds like the computer isn't coming out of cold start. Do all the plugs look the same? What controls the fuel pressure on a 280? To much fuel pressure, could be a problem.

 

[Rule for you]

Thanks for the reply Dobmoney, I will get him to check all of the issues you mentioned.

2 of the plugs might not look as fouled as the other 4. By the way I have a Grand Sport like yours, white with yellow . I had a 1992 PM 225 and for the last 15 years a 2003 GS with be this 280

 

[Rule for you]

Is your butterfly on the horn set to 0.0005 to 0.0006 at idle ,also I use the h8 plug instead of the H9 it runs hotter

I will get my Mercury mechanic to also check the butterfly setting on the horn, and may try the hotter plug, Thanks for that info also, "brund"

 

[Rule for you]

I will confer with the mechanic next week about all the troubleshooting I have received from all of y'all. Thanks so much

 

[Rule for you]

2 of the plugs might not look as fouled as the other 4. By the way I have a Grand Sport like yours, white with yellow . I had a 1992 PM 225 and for the last 15 years a 2003 GS with be this 280

Sorry dubmoney, I got you confused with another member about what boat you have.

 

[eric turner]

I am having the same problem. What exactly are you doing to clean the plugs to get home

 

[SLOmofo]

I partly pull the spark plug wire/boot away from the spark plug making a gap that the spark has to jump before getting to the the spark plug. All spark plug brands are different as to how many ridges there are on the porcelain, on the ones I use I pull back the boot so 3 are now exposed. Guessing this is about an 1/8" gap between the plug metal end and the wires metal end. What this does is requires the coil to produce/build up more energy to bridge the added gap and then jump the spark plugs gap. This works as long as the coil can produce enough energy and the spark doesn't find an easier path to ground.

 

[ssv1761982]

I partly pull the spark plug wire/boot away from the spark plug making a gap that the spark has to jump before getting to the the spark plug. All spark plug brands are different as to how many ridges there are on the porcelain, on the ones I use I pull back the boot so 3 are now exposed. Guessing this is about an 1/8" gap between the plug metal end and the wires metal end. What this does is requires the coil to produce/build up more energy to bridge the added gap and then jump the spark plugs gap. This works as long as the coil can produce enough energy and the spark doesn't find an easier path to ground.

Not many of us old timers left that know some of the "little" tricks!

 

[SLOmofo]

That's "older" sir. I was a grease monkey all my working life. Another is throw all the plugs in the campfire over night and let them burn off. An ignition coil will only put out enough to discharge. Up the requirement, then a hotter spark will be produced. Electricity just like water seeks the path of least resistance. Easier to flow down a fouled porcelain then jump a gap.

 

[THutch]

I used to have the same fouling problem with my 280. Now, as soon as I come off plane and idling, I trim up. No more problem. These motors do not idle well. Trim up, idle all day. I’d try that first before you burn more time chasing this problem. If you plan to idle and search for fish with graphs, get another motor. 280 isn’t for fishing in my opinion.

 

[gmorgan]

I have always thought I’d love to have a 280, and I still believe that, but (drum roll) it would only be with 260/Drag electronics. I like to be able to work on my own motors, and I’m clueless on the 280 style electronics.

 

[Bill Mason]

Been running 280 many years. If you are running champion plugs you will have this problem. Even one will cause problem. check other items guys have mentioned also. Good luck