Engine is full throttle when starting....HELP!!! 79 Johnson 140 HP

[Airxsteel]

HELP

Ok, big problem today on the water.

You know it is going to be a bad day on the water when you forget the boat key...

So after I get the boat key....from my wife .....who brings it to me at the lake.....

I get in and start it up. Well as soon as it turns over, it starts up and acts like I have the throttle all the down. So it revs up all the way as if I got the hammer down on it. I quickly shut it off, then try it again. Same result.

Ok, now last time I went to the lake, which was last week. I had no problems.

Here are the things that did change:

1. I put on a new SS prop.
2. The throttle tension knob on the control box unscrewed and fell off. It worked however that day last week and I didn't think nothing about it since it was working ok.

I don't think the prop had anything to do with it , since all that had to deal with was the lower unit.

I think the throttle is stuck somehow and it isn't letting me throttle down the engine. I tried to see if it was stuck under the hood somehow, so I lifted it and made sure that it could move (shift cables to throttle) and they were moving back and forth ok, not stuck.

I then tried to move the throttle back and forth at the control box, and I could see the cable moving the throttle at the motor.

So if it is stuck some kind of way, I don't have a clue why or how.

Any advice on this would be much appreciated. Talk about a bad day fishing.

[luvdmymerc]

You have a problem in the trottle linkage somewhere. Take the cowling off of the motor
and watch the linkage when you throttle up & down. Should be easy to track down.

[ChampioNman]

Pull the cowl and pull the cables off at the linkages. Start the motor on muffs, if it races to 5K wit everything set to normal on the motor then,,, you need to check timing.

[Airxsteel]

So the linkages I am assuming here are the throttle cables that actually connect or "Link" to the motor. If I pull that all off, then it should not be telling the motor "I need more gas".

If it works, and it runs normal after pulling off cables at the linkages, then what then? Do I need new throttle cables or a new control box?

If it doesn't work, you guys mentioned the timing. Is that left to a mechanic? What would that cost a fella?

Thanks by the way, you guys are quick and very knowledgable.
Eric

[SEAHORSE]

Remove the air silencer cover and inspect each of the throttle plates. They should be closed completely at idle. Make sure none are missing the mounting screws and that there is no sticking or stiffness in the throttle shafts.

I have seen motors than injested a piece of motor cover foam, bolts, low flying birds, etc. that kept the throttle plates from closing.

[Airxsteel]

That is a good point SEAHORSE. I will check that. The foam on my cover is old and crappy , so no telling what is in there, maybe Jimmy Hoffa.

[Brokemotor]

timming stuck?

[Airxsteel]

Remove the air silencer cover and inspect each of the throttle plates. They should be closed completely at idle. Make sure none are missing the mounting screws and that there is no sticking or stiffness in the throttle shafts.
I have seen motors than injested a piece of motor cover foam, bolts, low flying birds, etc. that kept the throttle plates from closing.

That is exactly what it was. A bolt was blocking it, and making it wide open. Took out the bolt, cranked up fine.

Now how in the world do you rethread a screw? The bolt that holds the carbs on, will not screw back in the hole. There are no threads in side of it.

[1993392]

I suggest you don't run the engine until you locate ALL of the hardware. If your motor ingests a nut, washer or other metal, you will be making extensive, expensive repairs.

[Airxsteel]

To late. Already cranked it up. There were no other parts to it that I could see. I looked it over pretty good while I had it open to make sure. The bolt has no nut at the end of it, ( which I don't understand that , what keeps it there and not vibrate out anyway ).

When I cranked it up it ran fine , no weird noises or grinding of any kind.

[ChampioNman]

Sure that bolt isn't from the airbox cover, the carbs are held on to the mainfold by nuts.

[Airxsteel]

Yea, I checked it out. There are five bolts holding the airbox cover on and they are all there. Believe me, they are on there tight. Took alot to get that stupid thing off, especially the bottom one. Heck of a time getting that one off.
Four on each corner and one in the middle of it.

You can see where this screw fell out, it is all stripped out.

[Bassmeister]

It's not a screw that was holding the butterfly in is it? Make sure all the screws are in that butterfly, wouldn't hurt to check em all for tightness. You can get a new one from dealer and locktight it in. Just a thought.

[SEAHORSE]

If it was a throttle plate (butterfly) screw, then most likely a dealer would have a hard time finding the part number. Never fear, it should be #312852 if my notes are correct.

The throttle shafts are brass so use locktite and thread it in carefully. They are supposed to be "staked" which means they should never come out. You can use a vise-grip pliers on the head and on the end of the screw and squeeze hard to flare out the end so it can not come out again.

[Airxsteel]

Not the butterfly screw , it was the screw holding the plate with the carbs on it. It all connects to the air intake cover.

[Airxsteel]

Here are some pictures of it. This first one is looking down on it, and you can see the carb in the middle and on both sides it is suppose to have a screw to mount it to the air intake box. The one screw on the right is there, but the one that got ate and is striped is the one on the left. You notice there is no screw there now.




This one shows it pretty good how the screw is missing. Shouldn't there be a gasket between the carb and the air control?