78 Johnson 115 Idles at 2500 to 3000.

[madolive3]

Back again, my old engine idles way too high. I had this problem before I rebuilt the carbs as well aas fuel pouring out of the choke plates. well now the fuel problem is solved but I can't get the idle down. I have a FSM from 78 for this motor and I've done the carb adjustments and the throttle is all the way closed. I can find nothing in the manual about adjusting the low or high speed needles.
I'm thinking either too much fuel pressure or low speed needle adjustments. I'll continue to search. Thanks again.

Edit. My manual states that my carb has 'fixed low and high speed orifices, I don't think I have adjustable needle valves.

 

[emdsapmgr]

Re: 78 Johnson 115 Idles at 2500 to 3000.

That's correct-no idle adjustment needles. The 1971 carbs were the last V4 carbs with the idle adjustment screws. Once you get your carbs sync and linked per the service manual, the idle rpm's are actually set by adjusting the idle timing. That timing is what sets the idle rpm's. Idle timing is set by adjusting the large screw on the spark advance lever. If you unscrew it, the idle timing will be decreased, reducing the idle rpm's. For exact setting, probably best to disconnect the throttle cable at the engine end to make sure your cable is not binding.. You need to make the idle adjustment when the boat is floating normally in the lake and is in forward gear. Set the idle for 650-700 rpm's. You can't set the idle on the trailer.

 

[laotou]

Re: 78 Johnson 115 Idles at 2500 to 3000.

You need to make the idle adjustment when the boat is floating normally in the lake and is in forward gear. Set the idle for 650-700 rpm's. You can't set the idle on the trailer.

Are there any tricks to set idle speed when the motor is in gear on the water? The boat is moving and I am alone. My engine is 1976 86HP Johnson. The idle speed is 1200 rpm in gear on the water. If I lower it to 900 rpm, the engine will die.

 

[emdsapmgr]

Re: 78 Johnson 115 Idles at 2500 to 3000.

Laotou: Tie the boat to the dock and put it in forward gear. It won't go anyhere, or just go out in the middle of the lake. If your engine dies when it gets down to 900 rpm, possible you have a fuel restriction in th idle passages of the carbs. At 1200 rpm, the carb butterflys may be slightly ajar (open) which will permit the engine to run on fuel from the mid or high speed jets instead of the idle jets only. At idle, the carb butterflys must be closed so the carb draws fuel from the idle jets only. You may need to pull the carbs apart and clean the idle passages so they will flow fuel properly.

 

[madolive3]

Re: 78 Johnson 115 Idles at 2500 to 3000.

When you say carb butterflies, do you mean the choke plates should be closed at idle?

 

[madolive3]

Re: 78 Johnson 115 Idles at 2500 to 3000.

emdsap, Thank you, It was timing, My throttle cable and carb linkages were way out of wack and it wasn't allowing the timing lever to retard all of the way.

 

[laotou]

Re: 78 Johnson 115 Idles at 2500 to 3000.

Tie the boat to the dock and put it in forward gear.

Thank you, emdsapmgr. Next time, I will tie my boat to the dock and put the gear in forward to see if I can tow the government property away. LOL.