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Mercury 3.3 hp won't start

D

Davoh

New member
I have a 1997 3.3hp Mercury that refuses to start. A little background is in order; I motor was running perfectly 2 days ago, and on taking it out again I could not start it and it was backfiring during cranking through the exhaust. I did the following:

Removed spark plug and checked the spark - its OK

Plug is wet when removed

Removed the fuel and replaced with fresh

Removed the carby it was in a very good condition but pulled apart and cleaned anyway

Tried to restart not firing at all. Checked the spark plug again still has spark

I live in Noosa Heads, Australia the motor does not get stored, I use it all year round.

Any help appreciated
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I assume that's a one cylinder motor? If the plug is getting fouled, it won't go--period. (That's the nice thing about multi-cylinder motors; the other plug might get it going.)

I suggest pulling the plug--clean it with lacquer thinner--spin the motor over good to blow the gunk out, then put the plug back in and try again. You might need to do this a few times. And it that doesn't work, try some ether (starting fluid).

Jeff
 
Hi Jeff,

Yes it is a single cylinder and I have cleaned the plug several times and blown the any thing out of the barrel. Still no go.

davoh
 
I though about the flywheel key but I am getting spark at the plug and the cylinder is moving up the bore. If the key was sheared would this happen??

Davoh
 
The back firing would indicate spark at the wrong tiime.----With a sheared key the ignition timing could be way out.------And it takes very little effort / no money to check the key !
 
Ok, I will check the key and see if it's sheared. Also buy a new spark plug although it is not that old but the spark was not blue more orange colour.

I will report back on my result as soon as I can get back to the motor.

Thanks All

Davoh
 
Good call on the flywheel key, I had this problem recently with a motor. It would almost start every pull. Finally got a brain and checked it and sure enough. Ran perfect after that. The fact that it ran perfect a couple of days ago and now will not as well as backfires would definitely a gooood reason to check the flywheel key. Make sure you completely pull the flywheel, not just look under the nut.
 
Well it was a struggle but finally pulled the fly wheel off, the key was intact not burred, perfect really. Now for a new plug, I will be dirty on myself if that is what was the problem.

Davoh
 
I know this post is over 10 years old but it's incomplete. I have the exact same problem and key intact. I'm wondering if it could be the timing sensor instead. Getting fuel compression and spark, no start only a few backfires.
 
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