1972 Mercury 650 Thunderbolt 65 HP ...Extra Spark on cylinder #1?...

franklenz

Petty Officer 3rd Class
Joined
Jul 24, 2013
Messages
76
On my motor listed above, I was setting the link and sync - no major issue.

But, when I was manually turning the flywheel with a timing light on the plug wire #1, the trigger would send an EXTRA spark to cylinder #1 about an inch before the belt alignment mark - I'm guessing that this would be somewhere around 40-60 degrees btdc. The trigger would send a normal spark at 0-2 degrees btdc as it should. This only occurs on cylinder #1 - none of the other plugs seem to be affected. It is a real strong and loud contact too - more so than the regular trigger marks or contacts.

I doubt this is normal, unless it's for very low rpms to help start the motor - which I doubt very much.

Any clue as to what would cause this? And, what to fix or check?

The motor runs fine in and out of the water, but if #1 is getting an extra spark (which does not appear to happen at decent rpms, and I have a ruff low idle in gear in the water, but who knows) I don't want to blow my #1 piston.

I'm thinking that I need to look at the cdi, or the rotor.

Please let me know what you think....

Here is a video of the motor in the water - notice how it's rough between the hole shots.

https://youtu.be/ZXgh2OtwtlU

https://youtu.be/L-vRLJnRIs8
 

franklenz

Petty Officer 3rd Class
Joined
Jul 24, 2013
Messages
76
Oh... forgot to add... when motor is running and I'm using the timing light on any of the cylinders, the light only flashes one time per revolutions. I don't see that extra spark - it only happens when I'm manually turning the flywheel.
 
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