63 40hp Johnson won't run without choke on?

[scochran2]

I have a 1963 Johnson 40hp on a '61 SABER 14'. It starts and runs good, until it warns up. When the choke is opened it bogs down. Runs from idle to half throttle fine, low speed adjust react, choke works on auto or open. Go past half throttle and it bogs down and will die, pull the choke lever to closed and it will run to 22 mph. The longer it runs the slower it start to go. after about 20 minutes, it's down to 6-8 mph wide open. I figure this is due to spark plug fouling, they turn black and appear wet when removed. My first idea is blocked exhaust, put 3oz. of carb cleaner in 6 gals. and ran for 30 minutes, no change. Have checked carb. high speed jet is clear, needle/seat new, float good.

 

[JB]

Re: 63 40hp Johnson won't run without choke on?

Hmmm. Carb looking good? You have an obvious case of fuel starvation, for which your carb is the prime suspect.<br /><br />Blockages in the high speed circuit don't usually occur in the jet, they occur in the passages from the jet to the throat.<br /><br />I think your carb needs a thorough cleaning and blowing out.<br /><br />Good luck.

 

[scochran2]

Re: 63 40hp Johnson won't run without choke on?

Thanks for the reply. I blew carb cleaner through the passages from the jet to the throat, seemed clear. What about the fuel pump? I'll pull the carb again to be sure.