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2001 Johnson 150 missing at high rpm

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Bassone75

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New to this site so thanks in advance to those willing to give advice! 2001 Johnson carb motor, had carbs rebuilt, chris Carson reeds, new ngk plugs, new plug wires, all new fuel lines and primer bulb, compression on all cylinders mid 90's which I know is a little low for this motor. Starts great, idles great, gets on plane great but when I get to high rpms it
will start to miss, kinda sounds like it's loading up, you can hear a big diffence in the sound of the motor, I can let off of the gas just a little and it will level out. It once I get back to high rpms again it will do it again, only does it around 52-5500rpms does this sound like cab flooding, or some time of electrical issue, could the carbs not be set right? Any help would be great l, again thanks
 
Hook up a timing light to # 1 cylinder.----------Take motor to full throttle on the lake.----Observe light when motor falters.-------Repeat test with other 5 cylinders.-------You may be able to identify a spark issue that way.
 
I don't want to sound like a stickler here, but I've only ever run OEM spec spark plugs in my Johnson/Evinrude engines. NGK makes a fine plug and that's what I use in my jet skis, but again those are the OEM spec plug for those engines. Reliability and clean operation have never been a problem when I use the spark plug spec'd out for the engine.

Your engine calls for Champion QL78YC plugs. http://www.marineengine.com/newparts/part_details.php?pnum=CHAQL78YC I've found these in the marine section of my local Wal-Mart, online here at Marineengine.com for $4/each, or other online sources.

I'd suggest installing a new set of these plugs properly gapped and give it another run. Obviously this 'parts swapping' to diagnose an issue. I always buy used stuff and when I'm trying to track down a mechanical issue my first order of business is to determine which incorrect parts the previous owner has installed. Once that's corrected I can go back to ground zero and diagnose the problem.

KJ
 
Only reason why I put those plugs in is bc everyone around here has told me those plugs are the best! I will try the champ just to see sure, that's not much to buy those. Thanks for your help
 
kevinj said:
I don't want to sound like a stickler here, but I've only ever run OEM spec spark plugs in my Johnson/Evinrude engines. NGK makes a fine plug and that's what I use in my jet skis, but again those are the OEM spec plug for those engines. Reliability and clean operation have never been a problem when I use the spark plug spec'd out for the engine.

Your engine calls for Champion QL78YC plugs. http://www.marineengine.com/newparts/part_details.php?pnum=CHAQL78YC I've found these in the marine section of my local Wal-Mart, online here at Marineengine.com for $4/each, or other online sources.

I'd suggest installing a new set of these plugs properly gapped and give it another run. Obviously this 'parts swapping' to diagnose an issue. I always buy used stuff and when I'm trying to track down a mechanical issue my first order of business is to determine which incorrect parts the previous owner has installed. Once that's corrected I can go back to ground zero and diagnose the problem.

Do you know what the proper gap is for these plugs for this engine?
Click to expand...
 
Bassone75 said:
Do you know what the proper gap is for these plugs for this engine?
Click to expand...
How about this for a handy reference. http://www.marineengine.com/parts/champion/outboard/johnson-outboard-spark-plug-guide.html

Looks like 0.030" is the correct gap.

Your friends are right, NGK does make a great spark plug and they work fantastic in the correct applications. Personally I've found that the properly spec'd Champion plug is just about flawless in Johnson/Evinrude engines.

I had a friend that was on vacation and fouled an NGK plug in his jet ski. He went to a local auto parts store and the guy gave him a plug that was a higher heat range saying "here, this hotter plug will really make her sing". It sure did, until the piston dome got too hot and melted a hole right in the middle of it. :mad: When it comes to spark plugs I just don't like to mess around so I always use what the OEM says is correct.

KJ
 
Awesome! Thank you for your help, I will put the other plugs in and gap them correctly! Worth spending 30 to see if it fixes my problem, again thank you!!!!
 
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