1961 Johnson 40 hp... Unable to achieve top end running speed

[1930 AA]

Greetings
Took the boat out today after having performed the following:
1. Completely rebuilt carburetor
2. New fuel pump
Engine idles smoothly
Does not appear to be misfiring
Navigating through a no wake zone is problem free
Once out in the clear ...as throttle is advanced RPMs increase but dramatically fall out at nearly full throttle.
With the wife driving I pulled off the engine cover and placed two of my fingers over the carb intake and the boat took off like a scalded cat.
The placement of my fingers was obviously mimicking the action of a choke thereby increasing the richness of the fuel mixture.
Anybody got some advice for me?
Thanks a million if you do!!

 

[Joe Reeves]

Re: 1961 Johnson 40 hp... Unable to achieve top end running speed

Manually clean the high speed jet that is located in the bottom center of the float chamber... way in back of that 7/16" slotted drain screw.
Your explanation indicates that the jet is somewhat clogged which is resulting in a fuel restriction. The two finger choke scenario is forcing fuel into the intake manifold via another route.

 

[1930 AA]

Re: 1961 Johnson 40 hp... Unable to achieve top end running speed

Thanks for the quick advice.
I will tackle that fix this evening after work!
Cheers.

 

[1930 AA]

Re: 1961 Johnson 40 hp... Unable to achieve top end running speed

Great advice!!
Followed your guidance and discovered copious amount of rusty debris clogging the orifice.
Runs like a champ now.
Thanks for the help

 

[Joe Reeves]

Re: 1961 Johnson 40 hp... Unable to achieve top end running speed

I knew you could do it.