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Engine misfireing

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dmiller532

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Help! I have a 1981 Mercury in

Help! I have a 1981 Mercury inline 6 motor that is misfiring - running rough with a little more then idle speed max throttle or it will die out. I was traveling down the lake at full throttle when all of a sudden I lost power. I am not a boat motor machanic but I would like to try trouble shooting the problem myself. I beleive I lost spark going to some of the spark plugs but I do not know how to check for this. It has 2 what I would call spark packs. I think maybe one of them is bad.Can somebody help me with this issues. Your responses will be greatly appreciated.
 
Start the motor and use an ind

Start the motor and use an inductive pickup timing light.Clip it on one wire after another-----no flash means no spark to that cylinder.
 
I have a 2004 merc 115 efi. at

I have a 2004 merc 115 efi. at sea level it runs fine. when I go to a lake at 2200 feet it won't accelerate. any suggestions?
 
"Donald, you should have start

"Donald, you should have started a new discussion.

Anyhow, an EFI is not like a carb'd model. With a carb you re-jet to compensate for the elevation.

Your engine computer should be doing that for your motor and recalculating the air/fuel mix.

However, the air fuel mix is only part of the equasion.

Merc built "high altitude" models in earlier days. In addition to different jets they also had lower gears so it was easier for the motor to turn the prop in the thin air where the motor couldn't breathe properly.

Since you are not likely to swap out gears, perhaps you are going to have to try going with another prop with less pitch so that the motor can get it turning instead of gagging out when you hit the throttle..."
 
"Ikia,
Thank you for your res

"Ikia,
Thank you for your response on how to check my motor. I will use your technical advice on how to trouble shoot my motor."
 
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