Idle Speed on 140 '83 Johnson

[jayhunt3]

Need help determining the right idle speed for an '83 140 Johnson. Once the engine is warm it idles at 12 to 13 hundred rpm but sometimes it kicks down to 5 to 6 hundred. In forward the lowest rpm is 5 to 6 hundred. Where should the idle be set for normal conditions and should it be kicking down to 5 to 6 hundred? At that low rpm it is hard to shift into gear without stalling the engine. Thanks

 

[R.Johnson]

Re: Idle Speed on 140 '83 Johnson

If the engine is in proper tune, and sync it should hold a steady 750 rpm in gear.

 

[jayhunt3]

Re: Idle Speed on 140 '83 Johnson

Thanks for the post. What should the rpm hold at out of gear and warm?

 

[R.Johnson]

Re: Idle Speed on 140 '83 Johnson

Your tach will probably show about 900-1000. Not all tachs are accurate at this range. I go more by how the engine shifts, and sounds. The main thing is you do not to put strain on the shift dog, and forward gear.

 

[ob]

Re: Idle Speed on 140 '83 Johnson

Duxman,A factor to consider between the difference in RPM that your engine will run at idle out of gear verses at idle in gear unrestricted is dependent upon the load that your engine is pushing and how the setup is propped.Example: if your engine is over propped there will be a greater difference between the in gear idle and out of gear idle rpm.What is your engines WOT rpm capability as propped?

 

[jayhunt3]

Re: Idle Speed on 140 '83 Johnson

OB - Thanks for the reply. I understand that various factors such as weight and prop pitch will influence the rpm in gear. I am trying to get a feel for the proper rpm out of gear that will allow for good shifting without a stall or undue pressure on the drive line.

 

[ob]

Re: Idle Speed on 140 '83 Johnson

Which was my point.If you find that in order to hold your "in gear" idle rpms at the minimum range,(650)you may find that you need to set the out of gesar idle at a dangerously high(1200-1300) rpm.Bare in mind that the out of gear rpms will be a bit higher when running engine on the hose as opposed to having it submerged in water.Final idle speed adjustment setting is factory specified with the engine in water,in gear,with the boat moving unrestricted.<br /><br />Engine dying on throttle up when shifting into forward gear from neutral is caused by one or more of several things.Restricted and or too lean adjustment of idle orifices,engine overpropped,carburetor link and synch out of adjustment.

 

[jayhunt3]

Re: Idle Speed on 140 '83 Johnson

Ob - Thanks for the thoughts. This engine is a rebuilt 140 detuned with a 115 carb. It has an SS prop that I had on a 115 rude without problems. It may be advisable to switch back to a stock al. prop. How can I tell if the prop is to much for this engine/boat combination?

 

[ob]

Re: Idle Speed on 140 '83 Johnson

WOT rpms should be in the neighborhood of 5500.This will afford the best all round performance from your setup.

 

[ezeke]

Re: Idle Speed on 140 '83 Johnson

OB, you are the man!

 

[R.Johnson]

Re: Idle Speed on 140 '83 Johnson

What do you mean by a de-tuned 115 carb on your 140 engine? Why would you do this, what is the point? Your engine propably failed due to a lean mixture. Are you saying that you want to lean it out some more. What do you mean by a detuned carb? This is new to me.

 

[jayhunt3]

Re: Idle Speed on 140 '83 Johnson

R.Johnson - This 140 was rebuilt using a carb from a 115 hp. engine and thus only generates 115 of power not 140. This is what I meant by detuned although I realize it is not detuned in a literal sense.