2001 Johnson doesn't go higher than 2500-3000rpm

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May 19, 2012
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Johnson 115 will not go fast, barely on plane, or sometimes not at all.

It will start surging, I guess you would call what it's doing.

I tried putting in a new thermostat on each side using one new one and switching guessing it would only be one or the other causing the engine to go into S.L.O.W. mode.
But it wasn't :(

There are no alarms or lights going off btw

I need help!!!

Thanks
 

James R

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Feb 1, 2007
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2,660
Re: 2001 Johnson doesn't go higher than 2500-3000rpm

Surging suggests a fuel supply problem or miss firing on one or more cylinders. Does it idle correctly or is it lumpy. If it is not idling correctly
Pull each plug wire off in turn until you find one or more cylinders that do not change the motor rhythm. You will then need to do a spark test to determine if you have a spark on the offending cylinders. If you have sparks and the plugs are old it may just be new plugs needed.
A compression check would be helpful to eliminate a problem in that area. Next question is, when were the carbs last stripped, cleaned and rebuilt with new kits.
If the fuel pump is at fault, squeezing the primer bulb, with the engine at the struggling point, will cause the engine to power up, providing there isn't a blockage at the tank.
 
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Re: 2001 Johnson doesn't go higher than 2500-3000rpm

It seems to idle very well.
I was just out and did a spark test and all have a spark.
Also I replaced the spark plugs earlier this week. Should I still try to pull the wires off the plugs to see if it doesn't change motor rhythm?
I don't have a clue when the carbs would have been pulled out last, but I wouldn't be surprised if they never have. I just got this boat and motor in the beginning of May and ran flawlessly until the end of June.

Since you mentioned it, I have tried to pump the bulb while running and it seemed to want to stall out, granted I wasn't going for full throttle because I was the only one in the boat at the time and didn't want to fall out, haha.

I do have a video of it if anyone has a good ear and if it would be helpful.
Tach
Surging Outboard-Hole Shot-Tach View - YouTube
Engine
Surging Outboard-Hole Shot-Engine View - YouTube
 

boobie

Supreme Mariner
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Re: 2001 Johnson doesn't go higher than 2500-3000rpm

What's the compression on it and have you done a cylinder drop test on it to see if it's running on all 4 cylinders ??
 
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Re: 2001 Johnson doesn't go higher than 2500-3000rpm

To answer your question, I don't have a compression tester, and I'm not sure exactly how to do a cylinder drop test unless it is the same thing as as what James said , where you would disconnect one plug at a time to see if one doesn't change the rhythm of the engine.
- sorry for my in expertise. Haha

I have to say that when starting the engine cold and running it, I can get it to full throttle but after about ten minutes of running it will go into that S.L.O.W. mode. Still not sure if that's what it is due to the fact that there are NOT any alarms going off.
 

boobie

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Re: 2001 Johnson doesn't go higher than 2500-3000rpm

Disconnecting one plug at a time is correct.
 
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Re: 2001 Johnson doesn't go higher than 2500-3000rpm

Compression came out great well within 10% on each cylinder. And on the drop test, every plug wire I pulled, the engine suffered a little from it.

That's good right?


What can I test next?
 
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Re: 2001 Johnson doesn't go higher than 2500-3000rpm

I ran another test today and put the engine at about 3000 revs where It starts to surge and then I pumped the primer bulb. I went back to the throttle then hit it, and it seemed to work pretty well, an occasional, what I'll call a "miss" or I guess a surge, happened, but I would have to keep primping the bulb to keep it up at WOT.
 

Chris1956

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Re: 2001 Johnson doesn't go higher than 2500-3000rpm

Check for air leak in fuel line, clogged filters, clogged main strainer under the airbox.
 
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Re: 2001 Johnson doesn't go higher than 2500-3000rpm

I have checked for air leaks,those were fine. Fuel filter, I just had replaced. Not sure of a main strainer, but I did pull out a carb, and looked like new and no gasket wear.

Also, this morning, I took out the VRO and inspected it, looked very clean, no gasket wear there either, really well taken care of engine.
 

pn

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Re: 2001 Johnson doesn't go higher than 2500-3000rpm

looks can be decieving, take another look at your vro.
 

Chris1956

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Re: 2001 Johnson doesn't go higher than 2500-3000rpm

The main strainer is a white plastic knob, on the fuel bracket, under the airbox. If the gasket leaks air in, that can interrupt fuel flow. If the strainer is clogged.....
 

James R

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Re: 2001 Johnson doesn't go higher than 2500-3000rpm

I had one instance that drove me crazy. Symptoms were the same as yours. It was a problem with the lower unit. I did not have the opportunity to strip the lower but a good used unit cured the problem. Craaaazy.
 
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