1978 Johnson 85HP Javelin idles too high unless manually adjust throttle arm

[superharmonix]

Hello all. When I start my motor it is already at a very high idle. I can manually push the throttle arm back at engine and it idles back down properly. When I put in gear and then back to neutral, idle speed does not decrease accordingly. Instead, the idle speed barely backs down and when I am in neutral, the idle is WAY too high. The trunion screw is all the way screwed in as tight as it will go and it seems like if I had another inch and a half or so on that trunion I would be able to fix the problem. The bottom arm of the throttle control and the arm on top, connected by a spring, seem to move slightly independently of one another. It's as if when I back off the throttle the arm does not want to move back all the way. Short of driving around the lake with the cover off and manually readjusting wevery time I decide to shift into neutral, any ideas? Thanks a bunch, driving me nuts!

 

[emdsapmgr]

Re: 1978 Johnson 85HP Javelin idles too high unless manually adjust throttle arm

When at idle the throttle butterflys are closed. Make sure the throttle roller is not touching the cam when at idle. You should be able to slip a pc of paper between the two at idle. Also, visually make sure the carbs are adjusted so both butterflys are completely closed at idle. The idle speed is adjusted by reducing the idle timing, not by carb adjustments. Turn the idle screw on the spark advance lever counter clockwise to reduce the idle timing. Idle timing varies between different boats that have the same engine, so adjust the idle so that you meet the idle rpms spec, not any idle timing degree spec. 650-750 rpm's when idling in gear, while floating normally in the lake.

 

[superharmonix]

Re: 1978 Johnson 85HP Javelin idles too high unless manually adjust throttle arm

I wish it were a carb thing.
If yoy look at my engine from starboard, the throttle cable attaches to an arm via nut, then that arm attaches to an upper arm via nut. in between these two there seems to be a bit of play.... most importantly as noted the engine will throttle up great, but then will not throttle down without manual adjustment....

 

[emdsapmgr]

Re: 1978 Johnson 85HP Javelin idles too high unless manually adjust throttle arm

Disconnect the throttle cable at the engine. What happens if you throttle up the engine with your hand, then let go. Will the engine run normally (return to normal idle) with the cable disconnected? You need to know if the problem is in the throttle linkage of the engine, or in the throttle cable adjustment.

 

[relocyo]

Re: 1978 Johnson 85HP Javelin idles too high unless manually adjust throttle arm

Well I have the same year and hp as you, mines a seahorse, I know from my own motor that it takes a long ***** time to warm up and it wants 2k rpm for a bit, but slowly reduces and idles at about 800 rpm on muffs, about 600 in the water with load... Just sayin from everything ive read about these motors are they are cold natured and take time, im just wondering if your giving it enough time to properly warm up... Just a thou gh t, and my throttle arm does have some play in it too...

 

[superharmonix]

Re: 1978 Johnson 85HP Javelin idles too high unless manually adjust throttle arm

I had the boat out on the water this weekend, and it still does it, but after it's all nice and warm and under a load in the water, the problem goes away. It's interesting how it idles so high without backing off in the driveway, but only does it for a bit on the water.

 

[superharmonix]

Re: 1978 Johnson 85HP Javelin idles too high unless manually adjust throttle arm

Disconnect the throttle cable at the engine. What happens if you throttle up the engine with your hand, then let go. Will the engine run normally (return to normal idle) with the cable disconnected? You need to know if the problem is in the throttle linkage of the engine, or in the throttle cable adjustment.

I have not tried this yet. Thanks for the tip. My money is on the linkage but we shall see! Thanks emd...I was born is Springfield, IL, by the way. ...lived in Lincoln, Alton, Galesburg...Oregon now but my wife and I just made a fantastic road trip back that way last summer. I saw you are from LaGrange so I thought I'd throw that in there...

 

[ThePigBuckler]

Re: 1978 Johnson 85HP Javelin idles too high unless manually adjust throttle arm

"Hello all. When I start my motor it is already at a very high idle. I can manually push the throttle arm back at engine and it idles back down properly. When I put in gear and then back to neutral, idle speed does not decrease accordingly. Instead, the idle speed barely backs down and when I am in neutral, the idle is WAY too high. The trunion screw is all the way screwed in as tight as it will go and it seems like if I had another inch and a half or so on that trunion I would be able to fix the problem. The bottom arm of the throttle control and the arm on top, connected by a spring, seem to move slightly independently of one another. It's as if when I back off the throttle the arm does not want to move back all the way. Short of driving around the lake with the cover off and manually readjusting wevery time I decide to shift into neutral, any ideas? Thanks a bunch, driving me nuts!"


This is exactly what is happening to mine. I'm bothered by the fact that the trunnion is screwed all the way in and it's still high. I pulled the cables and confirmed it's in the linkages. The carbs are returning to a full closed position(can fit a piece of paper in between the throttle roller and cam), but the timing advance lever is too far advanced, causing a high idle condition. It seems as if I grinded a little from the throttle lever/timing advance stop, I could get the advance to go back to where it should be, but I don't want to do that. The idle adjustment screw is all the way in and it's still 1/2" from touching the stop. What could cause the timing advance lever to be out of whack, is there an adjustment somewhere?

My goal is to get some adjustment back into the cable, and get the advance back at the same time.

 

[ThePigBuckler]

Re: 1978 Johnson 85HP Javelin idles too high unless manually adjust throttle arm

One thing to add. I did buy the manual and did a complete carb rebuild and link and sync on this motor since the floats were bad.