engine stumbles and dies

[Capt. Rich]

Here's one for the absurd. I did normal maintenance on my 2003 Mercury 40hp 2 stroke. I go to start and she instantly fires right up. Tell-tale pumping quite well. I let her run for about 10 minutes to check everything. I put the lid on and she dies. I try to restart and nothing. Turns over quite well but not even a pop. I take the lid off and she fires right up. I go to put the lid back on and bingo she dies again. I did this about half a dozen times. I check to see if the lid is hitting anything. I see no obvious interference by the lid. I tried the next day and she is still doing the same thing. WTF

 

[racerone]

Perhaps bad plug wires / sparkplug boots.

 

[bobbyc]

Perhaps bad plug wires / sparkplug boots.

To visually check for spark leakage.... try running it at night with the cover off

 

[fastjeff]

And in the darkness, so you can see any arcing.

Jeff

 

[Projectus]

Racerone - could this be a small exhaust leak suffocating good air? Or just a bad foam gasket on the cowling?

 

[faztbullet]

If running in a barrel yes it can dull in bad exhausted air

 

[Projectus]

I was thinking an exhaust leak more up near the engine - like a bad exhaust plate gasket. With the cowling on, and an exhaust leak, it wouldn't take long to replace oxygen with carbon dioxide and then no ignition.