40 HP Johnson rpm problem

[mmarino]

J40 TLCUD 1987. At almost all rpm ranges in the throttle, it is necessary for me to use the electronic choke on the key to keep it running at the appropriate rpms If I don't tickle it contstantly, about every 3 seconds or so, the rpms drop dramatically. If I get the timing just right I can keep it running wide open, but it is erractic. Thought it might be an elevation/jet problem, but after having had it out today at around 1500-1700 feet above sea level instead of 6 or 7,000 where I normally go, it acted about the same, poor. Problem is getting progressively worse. Thanks for your help in advance.

 

[Barnacle_Bill]

Re: 40 HP Johnson rpm problem

Check your fuel lines and especially the primer bulb to be sure all are soft and pliable and no cracks. If they are all good rebuild your fuel pump.

 

[tashasdaddy]

Re: 40 HP Johnson rpm problem

suspect the clogged carbs. fuel starvation.

 

[F_R]

Re: 40 HP Johnson rpm problem

Dirty carbs, especially the high speed jets.

Or, possibly a sneaky one: Timer base not going up against the stop resulting in retarded spark. Retarded spark plus carb throttle plates wide open equals lean running condition.

 

[mmarino]

Re: 40 HP Johnson rpm problem

Thanks a lot for the prompt replies. If it ends up being the carbs, do they need rebuilt or is there another way to clean them?

 

[tashasdaddy]

Re: 40 HP Johnson rpm problem

you are wasting you time and money if you don't do this.

http://forums.iboats.com/showthread.php?t=244013

 

[mmarino]

Re: 40 HP Johnson rpm problem

Thank you, if I need to work on the carbs, I will do that.
Appreciate all the help from everyone.