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Runaway johnnyrude

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Kyle cherry

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My boat has been sitting with bad gas for about 2 years. Couple weeks ago I brought it home and pulled the carbs off. It's a 1994 Johnson 88 with 2 double barrel carbs. I pulled them off, took them apart and cleaned them. Sprayed carb cleaner thru all the jets and valves and got all the gunk out. Cleaned the tank and replaced all the fuel line. Got it all assembled, primed it up and it took it a couple of times to start running but it finally did. Idles pretty good. But as I was easing the throttle up after letting it run for 15 minutes or so, when it got to a certain point of high rpm, it just runs wide open. I'll ease the throttle up very slowly and when it hit that certain point it takes off. What could be the problem?????
 
The problem is you. You are revving it in neutral, right? Don't do that. Someday you will hear a big bang as parts go flying everywhere.
 
kimcrwbr1 said:
Do you have it in a barrel of water or on the lake. If your running high rpm with the prop out of the water you can also damage the prop. If you are in forward gear on the water and it runs away the prop has a spun hub.
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i have the garden hose on it with the ears that go around the foot for the water pump. What would you recommend would be the best way to trouble shoot my problem? Barrel of water or back it into the lake. What's the best possible way to do it trailered
 
Kyle cherry said:
So you think my problem is just running it with no load on it? Just the carb kicking over to the high flow jets with no load? Put it under a load and maybe no more problem?
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Not even close to the high speed jets flowing fuel. But under no load your engine will run away on timing alone.

I serviced a 175 Johnson this year, the customer complained about the engine running away. While the engine was at idle in the water if you raised the rpm in neutral it would run up to 6000 rpm after you pulled the throttle back and would stay running after you shut the ignition off. The engine was so carboned up it would get a hot spot on the pistons and ignite the fuel and run away. The only way to shut it down was to kill the ignition and give it wide open throttle. I decarbed his engine and drained the low grade tcw-3 oil from his tank which was the cause. Johnson XD-50 only for your oil.
 
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Kyle cherry said:
i have the garden hose on it with the ears that go around the foot for the water pump. What would you recommend would be the best way to trouble shoot my problem? Barrel of water or back it into the lake. What's the best possible way to do it trailered
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AHA !!! Just as I said. Running it on the trailer on a hose presents exactly the same load on the engine as running it in neutral. The problem is you. But I'll take that back if you report back that it does it when in the lake where it was designed to run.
 
BTW, what you are experiencing is caused by flywheel inertia. Get that sucker spinning fast enough to overcome friction, and it will keep going with minimal power input.
 
fdrgator said:
AHA !!! Just as I said. Running it on the trailer on a hose presents exactly the same load on the engine as running it in neutral. The problem is you. But I'll take that back if you report back that it does it when in the lake where it was designed to run.
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Still does it :)
 
No I'm joking, ran great. Take it easy in me tho, I'm learning lol. Gotta learn a little as you go. Like my dad said, if you don't f up, you ain't learned shi*. Thanks for all the help guys!
 
kimcrwbr1 said:
Start another thread and be specific there are alot of different switches and plates but enter boat parts in your browser for generic boat type hardware.
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Also, just doing some after thinking, if that wouldnt have fixedthe problem, what would it be. Getting to a certain point on your throttle and then jumping to wot?
 
And when it idles and just kind of put puts around its runs a little rough, almost like a misfire but its not the plugs or wires. Just seems like its a little rough, what do you think could be the problem. When it wot it runs fine tho
 
Kyle cherry said:
Also, just doing some after thinking, if that wouldnt have fixedthe problem, what would it be. Getting to a certain point on your throttle and then jumping to wot?
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OK, I'm starting to get confused now. As I understand it, you are no longer experiencing a runaway condition in gear on the lake? But you are questioning what the problem may be if you were still having the problem? That is sort of hard to answer, since it doesn't happen. But if I may make one more comment on runaway. There are two basic causes, both caused by revving under no-load conditions. One is caused by compression ignition, when just the pressures in the combustion chamber ignites the fuel. Diesels and model airplane engines function that way. It technically is possible in an outboard, but pretty rare. The second is inertia, as you have experienced and is common when people rev them up on a trailer. Yeah, I'll take it easy on you, everybody has to learn somehow, sometime. I learned it about 60 years ago as an outboard mechanic when OMC "Big" 25hp motors got vacuum switches to prevent the situation.
 
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