Johnson qd-18 bump and pop

[blpierce76]

Hello everyone,

I recently got a hold of a Johnson QD-18 to use as a trolling motor for my boat. I found this site while looking for parts. So, I got the motor unstuck, replaced the spark plugs and adjusted the points. I got it to fire up, but while its idling it bumps hard enough to jerk the motor to the side and then it revs up a bit then slows back down.

I'm thinking it an issue with either the fuel system or the ignition. I do have a carb kit, new coils on the way (the plastic is cracked), and a water pump kit on the way from iboats - Thanks! I am hoping these fix the problem, but was wondering if anyone knew specifically what would cause this.

Hoping to have this beauty running soon. Thanks!

 

[bonz_d]

Re: Johnson qd-18 bump and pop

Sounds like your on the right track. Clean carb and assure you're getting good consistant spark and it should purrr like a kitten.

 

[HighTrim]

Re: Johnson qd-18 bump and pop

Could be ignition miss, could be lean sneeze. I wouldn't worry about it until you go through everything as both issues need attention anyways.

Clean and dress points, set to 020. I would install new plug wire when you do the coils. Are the condensors original?

Clean and rebuild carb, with fresh fuel lines.

Have you tested compression before spending money?

 

[kfa4303]

Re: Johnson qd-18 bump and pop

If the fuel/spark issues don't fix it, check the clutch dog. These old QD models are especially prone to having them wear out over time. Here's a handy link.

Johnson

 

[boobie]

Re: Johnson qd-18 bump and pop

Sounds like a bad ignition miss.

 

[blpierce76]

Re: Johnson qd-18 bump and pop

Could be ignition miss, could be lean sneeze. I wouldn't worry about it until you go through everything as both issues need attention anyways.

Clean and dress points, set to 020. I would install new plug wire when you do the coils. Are the condensors original?

Clean and rebuild carb, with fresh fuel lines.

Have you tested compression before spending money?

The condensors and points seem like they are fairly new. I'm not sure but they look like they have been replaced recently. I have cleaned the points and will set when I install coils. I have a carb kit coming to rebuild it.

I haven't tested the compression, but it did fire up and run, just had a bump and pull every now and then. I should have my parts today, so Ill let ya know if that doesnt fix it.

Thanks