2000 50hp Johnson 2 Stroke will idle, then die when put in gear and will not start again

KStoll14

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Aug 18, 2024
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I’ve got a 2000 Johnson 50 horse (J50PLSSM). I just removed the vro pump and put in a regular fuel pump that mounts to the side on the motor. I also replaced all fuel lines, new fuel filters, new CDI box, new spark plugs and a new carb kit and cleaned the carbs. Before it wouldn’t run for more than a couple seconds and now I got it running at idle pretty good on muffs. Backed it into the water to take it for a spin and it didn’t want to start. Finally got it started and put it in gear and it just died and would not start again. I have no idea what’s going on with it. Any suggestions of what to look for next would be greatly appreciated. Thanks!
 

saltchuckmatt

Commander
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Jul 19, 2019
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2,800
I think I'd start by isolating the control box and jump start it at the motor and see if it runs good that way. That will eliminate the control box.

Corrosion, bad wire, key switch.

Look at those things first.
 

jonesg

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Feb 22, 2008
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I’ve got a 2000 Johnson 50 horse (J50PLSSM). I just removed the vro pump and put in a regular fuel pump that mounts to the side on the motor. I also replaced all fuel lines, new fuel filters, new CDI box, new spark plugs and a new carb kit and cleaned the carbs. Before it wouldn’t run for more than a couple seconds and now I got it running at idle pretty good on muffs. Backed it into the water to take it for a spin and it didn’t want to start. Finally got it started and put it in gear and it just died and would not start again. I have no idea what’s going on with it. Any suggestions of what to look for next would be greatly appreciated. Thanks!
is it running on both cyl's ?
 

racerone

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Dec 28, 2013
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38,111
They run surprisingly well on 1 cylinder.----Post the results of a compression test.---Are both carburetors confirmed clean ?----Red lever on electric primer valve in the correct position ?--- -How did this motor run for you last season ?
 

KStoll14

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Aug 18, 2024
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They run surprisingly well on 1 cylinder.----Post the results of a compression test.---Are both carburetors confirmed clean ?----Red lever on electric primer valve in the correct position ?--- -How did this motor run for you last season ?
Had about 150 psi on both cylinders. Seems kind of high but not sure if it’s normal. Just had the carbs cleaned and a complete rebuild kit for both of them. A guy that has worked at a boat shop in the past did the work on that. Red lever is in the right position although I tried both positions for it. Also tried putting a new electric primer on it but that didn’t work. Have always had a slight idle issue with the boat since I owned it but now I can get it to idle fine but as soon as I put it in gear and it gets under a load it dies
 

jonesg

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Feb 22, 2008
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you haven't proved its firing on both cyls under load.
compression is excellent, carbs are rebuilt, great.
spark on both cyls is nice but you haven't proved its not dropping spark under load, a spark gap tester set to 3/8 inch will help.

so far the problem is a perfect description of an engine dropping a cyl under load, thats why we keep bringing it up.
 

KStoll14

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Aug 18, 2024
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you haven't proved its firing on both cyls under load.
compression is excellent, carbs are rebuilt, great.
spark on both cyls is nice but you haven't proved its not dropping spark under load, a spark gap tester set to 3/8 inch will help.

so far the problem is a perfect description of an engine dropping a cyl under load, thats why we keep bringing it up.
I will have to put it in the water and check that then. What would be the fix or thing to look for if it is dropping spark under a load? Also just found out the other day once it is idling and I put it in gear and it dies it is tough to get started again after a couple times. Not sure if that means something or just getting flooded or what?
 

KStoll14

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Joined
Aug 18, 2024
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Well figured out the problem. The CDI box or whatever it is called that hooks up to the coil to then send the spark to the plugs was apparently bad from the start. So I replaced that and took it for an hour and a half run last night and it worked good. That was the second new part that I have gotten that was junk from the start
 
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