1999 Johnson 15 hp stalls at low rpms.

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putzee52

Seaman Apprentice
Joined
May 25, 2008
Messages
31
So i picked this motor up in March from a dealer who tuned the motor before i picked it up. Had the boat out twice and it ran fine. Today it started a ran fine but when i throttled back to troll, it stalled and then would not idle without stalling. At wot it ran fine just now idle low speed.

When i got home i cleaned the fuel filter and checked the plugs. While running it in a bucket it stalled again. I then slowly adjusted the carb mixture which fixed the stalling.

My fear is that this is a temp fix. My fiend said the cold air when the motor was tuned in March compared to the warm air now messed it up. Is there truth to this? Or is there a bigger problem about to happen.
THanks
Jay
 
CATransplant

CATransplant

Admiral
Joined
Feb 26, 2005
Messages
6,319
Re: 1999 Johnson 15 hp stalls at low rpms.

That'll probably do it. You may have the idle speed set just a little too slow, as well. Running in a bucket is a lot different than running on the boat. There's more back pressure on the boat, since the lower unit is no doubt deeper in the water. There's an idle adjustment screw that bears against the idle stop on the carb. While you're on the water, pull the cowling and adjust, if needed, to raise the idle speed just a bit. But, your carb adjustment may have solve the problem already.
 
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putzee52

Seaman Apprentice
Joined
May 25, 2008
Messages
31
Re: 1999 Johnson 15 hp stalls at low rpms.

Thanks Cat

I have a wife 9months preg. I was seeing her in labor and me suck on the lake :eek:) Not that fishing would be a bad place to be stuck, I dont think i would be keeping the boat if that were to happen.

The dealer made all the engine adjusts before i picked it up, so i hope the weather made this adjustment be needed. This is my first boat so its all new to me. Will that screw need adjusting from time to time? Like i said the first 2 times i had the boat out things were fine.

Being it is used im sure the fuel filter cleaning and some Sea Foam wont hurt

Jay
 
CATransplant

CATransplant

Admiral
Joined
Feb 26, 2005
Messages
6,319
Re: 1999 Johnson 15 hp stalls at low rpms.

I hear you on not wanting to be on the lake with a dead motor when your wife goes into labor. I don't know how you'd explain that one away. :D

Unless the dealer did the adjustments on the water, he may have left it too lean. You really can't make the final adjustments until you're trying it on the boat in the water. Once you've adjusted it for smooth running, you shouldn't have to mess with it again until the carb gets cleaned the next time.

Dealers are also well known for setting idle speeds too low, for the same reason.

Dealers often deliver stuff that isn't set up perfectly, I'm afraid. There are many posts in this forum to that effect.
 
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putzee52

Seaman Apprentice
Joined
May 25, 2008
Messages
31
Re: 1999 Johnson 15 hp stalls at low rpms.

Would they have set that adjustment even when selling a used motor?

Also the unit i have is an electric start steering unit, does it have some sort of alternator to maintain the battery?
 
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