1973 johnson

[rosgood14]

i have a 1973 115 hp johnson. after i start the boat it runs fine but i would say every few min. it pops and you can tell that the prop slows down significantly. it goes for a few min. popping and then it will just completely die. no slowly dying like its running out of gas or anything. its going one sec then dead the next. when i have taken it out on the water it does the same thing but once it dies that first time it continues to die once i put it back in gear. need some help

 

[Joe Reeves]

Re: 1973 johnson

What are the compression readings of the individual cylinders?

With the spark plugs removed, at cranking speed, the spark should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it?

Checking the spark..... When doing the above test, if the spark is erratic, weak, none existent, remove the Black/Yellow wire from the powerpack and re-test the spark. If you now have proper spark, in all probability the ignition switch has a slight intermitent short, in which case replace it.

Also check that Black/Yellow wire (disconnected from the pack) for the slightest bit of voltage. Voltage at that wire will destroy a powerpack rather quickly. This type problem is also due to a faulty ignition switch.

This popping..... does it sound like a spitting back type sound like it might be coming from the carburetor section, OR is it actually a loud backfire shooting out the exhaust area?