Thread: backfiring mercury

what makes a 20 hp mercury backfire and not start when u are pulling the rope?also when pulling on the rope it will jerk back or stop turning the motor when pulling so hard that it will snatch u back

Sounds like incorrect timing to me. Check with a timing light and correct.

timing....or plug wires backwards..have you changed the plugs or a coil or something?? I know that sounds silly but its happend to LOTS of folks including me...lol. would be hard for timing to be that far off...possible...but hard. have you done something under the flywheel??? If the key under the flywheel has sheered off and the flywheel has moved some it will cause timing to out that bad. Just some thoughts on where to start looking. Something with timing...but for it to be that far out I think its more than an adjustment issue. Maybe a broke linkage or sometheing. Check it all out with a fine tooth comb!