94 johnson 120 v4 will not idle, running very rich

[jhicks79]

Ok. I'm a decent mechanic, but outboards intimidate me. I just bought a boat that has a 120 Johnson V4. This boat was very well maintained by the person I bought it from, but it has been stored since 2007. Motor started up once we primed it a few times, but it smokes really bad. I figured it was from sitting so long, and bad gas. Put in fresh fuel, ran it on the caps, and it turned by yard black for about 8' behind the prop. I took it to the lake to blow the crap out of it, and now it will not idle t all. When you are at no wake speed it smoke tremendously, and when you gun it, it takes a few seconds to clear out and go, then it sounds flat up to 5000rpm's. I know it's to rich, but how hard is it to adjust. I apppreciate any recommendations.

Thanks

 

[Daviet]

Re: 94 johnson 120 v4 will not idle, running very rich

You didn't list a model number, but below are a few thoughts.
The high speed jets are not adjustable, there are low speed needle valves.
Most likely you are going to have to go into the carbs and clean them up and install new gaskets.
What fuel ratio are you running, 50:1?
You might want to install a new water pump impeller if it has been sitting that long.

 

[Lil' Johnson]

Re: 94 johnson 120 v4 will not idle, running very rich

Make sure the red lever on the primer solenoid isn't open. If not, it sounds like maybe the needle and seat isn't closing all the way. take the airbox off and see if fuel is running out of any of the carbs. checking the plugs may give you some insight also.

 

[SparkieBoat]

Re: 94 johnson 120 v4 will not idle, running very rich

also check to see if you have a carb with a stuck open needle valve. 5000 RPMs at WOT is a little on the low side, should be closer to 5800. take the carb cover off and pump your bulb, fuel will run out of one of the carbs. trim the motor slightly forward.

 

[jhicks79]

Re: 94 johnson 120 v4 will not idle, running very rich

I had unhooked the oil injector, just because they worry me, so I'm mixing 50:1 in the tank. I pulled the carb cover off, and I did see some fuel under the left stack of carbs. As for the red lever, I'm not sure if it is open or closed. I did ajust the idle air mixture last night and made some progress. It would Idle fairly good for a minute or so, then it would load up and start to sputter. I'm leaning towards removeing the carbs and giving them a good cleaning, my only issue is I'm afraid of upsetting the butterfly angles. I don't want to make a small issue a big one by not knowing what I'm doing. I did notice that the inside of the carbs is spotless, but everyting is wet with oil and fuel mix. The mercury i had never did that. Thanks, for all you help.

 

[jhicks79]

Re: 94 johnson 120 v4 will not idle, running very rich

Ok. So far the marine shop has rebuilt the carbs, replace all the o-rings and seals on the intake, and ran up around a 1,200 bill. Still the same problem. The red lever on the primer solinoid was open. But when you close it, the motor will not idle at all. If you open the lever, it will put un burned fuel out of the exhaust(way to much fuel), and will run wot, but not good. Close the lever and it will not run. I admit at this point I'm completely lost...

 

[SparkieBoat]

Re: 94 johnson 120 v4 will not idle, running very rich

sorry to hear you have trusted an incompetent mechanic..it is very hard to diagnose this type of situation on a forum. If you are anywhere near Savannah GA, I will take a look at it for you and will not charge a dime if I cannot fix it.

 

[daselbee]

Re: 94 johnson 120 v4 will not idle, running very rich

Go back to the shop and ask them specifically what and how they cleaned the carbs.
Your symptoms of no idle with the red lever in the normal run position indicates that it is not getting gas at idle. There are brass tubes sticking down into the fuel bowl....they clog. See if you can get them to admit they did not clean those tubes. Also, there are passages that open up into the side of the venturi, right at the throttle butterfles. They are miniscule in size, maybe 5 thou size holes. They clog.
There are plates, or core plugs that must come out to clean those holes correctly. See if the core plugs look as if they have been off and new ones put in. If this has not been done, get your money back, and find a new mechanic.

Story here.....I was running my 96 200 looper (basically the same motor as yours, just two more cyls), and I do all the work on it. It was running good, then gradually started to run worse and worse, until it wouldn't idle at all. Pressing the key in made the engine pick up, and I could barely idle back to the dock by pushing the key just as it was trying to die.
I cleaned the carbs myself....couldn't be the carbs...huh? Wrong....it was the carbs. On two of the six carbs, the brass tube was completely clogged with what I have got to believe was salt deposits. And on all six carbs, the tiny holes into the venturi were clogged with the same stuff. This stuff built up over about a year's time....but I never would have thought it could do something like that in such a short time.

I wish I had thought to taste it. I bet it was salt deposits. Opened the holes up, now it idles like it should.

 

[jhicks79]

Re: 94 johnson 120 v4 will not idle, running very rich

I was thinking of doing the carb build myself, but I was a little intimidated. It was my understanding, the carb build used complete kits, which was supossed to replace all the jets, and tubes, but I can't say that for sure. I've done carbs on nearly everything else from dirtbikes to cars, but these worried me.

 

[SparkieBoat]

Re: 94 johnson 120 v4 will not idle, running very rich

you will either have to figure out how to DIY or find a trust worthy mechanic.