1975 7.5 Mercury Thunderbolt cranks and dies

BROUSSARD2 · Jul 10, 2019

I rarely work on Mercury motors, but the concept is all the same. I've run into an issue that I can't figure out. Any help is appreciated. Compression 120 both cylinders. Spark gap test fine. Rebuilt carb. New stator. It will fire right up, but the Rpms are really low. Runs for maybe 5 seconds and dies. I've tried spraying carb cleaner in the carb to see if it would keep it running it makes no difference. I've adjusted the mixture screw. I'm out of options. Any ideas?

oldman570 · Jul 10, 2019

You can check the flywheel key to see if it is partly sheared off causing it to be out of time. If the key is good , then get a manual that tells how to sink up the carb so it is set correctly. Also check the kill switch for any wire that might short out to ground

flyingscott · Jul 11, 2019

Are you using the throttle when starting?

BROUSSARD2 · Jul 12, 2019

I checked the half moon key. All looks good. I have tried using the throttle and without. Nothing seems to work. I don't think it's the carb through. I need to check the wiring though.