pulsating rpm while throttling up

[Alwsfishin]

1961 75 johnson....tuned up... rebuilt carb....rebuilt fuel pump....when I set the spark advance to specs, it will hardly run. When the gap that is set to .20 is opened up it runs better. Until I get to 2000 rpm & up the rpm bounces up & down. above 2000 it runs good. It also idles good at 600 to 800 rpm. I haven't had it near 4500 rpm, cannot seem to get it above 3500 despite running diff props. The boat is a 17 ft Lyman. Also new fuel line primer bulb & connect. 25 gallon tank under front seat is vented out the side with 1" line. I have another carb, should I rebuild it 1st then go from there. The high speed jets are set on this motor.

 

[Silvertip]

Re: pulsating rpm while throttling up

Sounds like you are not doing something right when setting spark advance. Have you checked the flywheel key to make sure its not partially sheared?