Johnson 120 gives trouble on plane

[keylime01]

Hello.<br /><br />I have a 1997 Johnson 120 outboard and when I get it up on plane it runs well for a good 5 or 6 minutes. Then, it begins to feel like the engine loses power like it's not firing two of the cylinders. If I bring it down and idle for a few minutes and then get going again, it's fine for a bit until it happens again. Any suggestions?

 

[Dhadley]

Re: Johnson 120 gives trouble on plane

Welcome!!<br /><br />When it does this, check spark. I would suggest a timing light. That way you can watch any cylinder and spot any that losses spark. That will pinpoint the issue. <br /><br />BTW -- we're not worried about what the timing is on each cylinder, just that the light keeps flashing.

 

[CATransplant]

Re: Johnson 120 gives trouble on plane

Consider overheating, as well.

 

[keylime01]

Re: Johnson 120 gives trouble on plane

Originally posted by CATransplant:<br /> Consider overheating, as well.

Thanks. What might be the causes overheating?

 

[Goodoleboy]

Re: Johnson 120 gives trouble on plane

Bad water pump and or cloged water passages in block. Does your over heat horn sound off at any time during your wot run or idel for that matter.<br /><br />If you haven checked the over heat horn for opperation. It could be you are over heating and you just dont know it.<br /><br />Good luck!