motor dies when slowing down to idle

T

TxHorns

Seaman
Joined
Jul 27, 2009
Messages
54
Sometimes when I have been going around 4000-4400 RPMs for a few minutes and back down to an idle my motor will die. I can be out for a few hours and it will only happen a couple times all day. Seems like the longer I have been going at cruising RPM's the more likely it is to die when I slow down.

I just got a new/used powerhead which is when it started happening. The motor is a 1992 Johnson 140hp. Any ideas on what could be the problem?
 
T

TxHorns

Seaman
Joined
Jul 27, 2009
Messages
54
Re: motor dies when slowing down to idle

Forgot to mention, once its dead, I usually have to turn the key a couple times before it will start. I don't know how it works exactly, but possibly something is sticking and the motor is flooding when I slow it down?
 
T

TxHorns

Seaman
Joined
Jul 27, 2009
Messages
54
Re: motor dies when slowing down to idle

Haven't been out for a few days but made it out today and its still doing it. When backing the throttle down, the motor kind of "stops off" at about 500 rpm before it dies.
 
jtexas

jtexas

Fleet Admiral
Joined
Oct 13, 2003
Messages
8,646
Re: motor dies when slowing down to idle

Worn carb float valves, can cause that, but nobody would install a powerhead without rebuilt carbs. Idle speed set too low is another possibility.

Are you throttling back suddenly while still on plane, so that the exhaust relief ports are getting submerged? Ever try coming off plane more slowly, before backing off to idle?
 
jimdd810

jimdd810

Chief Petty Officer
Joined
Mar 18, 2006
Messages
532
Re: motor dies when slowing down to idle

check your plugs and make sure they are gapped correctly and make sure the electrodes are all there in place. I had a 15 johnson that the electrodes were almost worn to nubs. it did the same thing it would run like a champ and as soon as I came of of wot the arn thing would die.
 
T

TxHorns

Seaman
Joined
Jul 27, 2009
Messages
54
Re: motor dies when slowing down to idle

Thanks for the advice! Put in new plugs and that did the trick.
 
jimdd810

jimdd810

Chief Petty Officer
Joined
Mar 18, 2006
Messages
532
Re: motor dies when slowing down to idle

Im laughing to myself a little not at your problems but the fact that im a marine mechanic and had that very problem myself. Oh well at least the carb is rebuilt and clean now (mine)
 
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