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115 hp mercury 1992 starts ok but cut out in gear

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yap_yap

Contributing Member
Motor runs well at start and will rev up in gear with ears on, but will cut out when put in gear on the water.
Have taken the carbs off and cleaned, put in new plugs but still cuts out when on the water.
Can some one please advise on what to check.
 
What exactly do you mean by cuts out??? Whats the RPM at idle??Have you checked to see if it has spark on all 4 cylinders? Is the sync and link correct??
 
There are no low speed mixture screws on the bottom 2 carburetors.------------------Report what you get on a compression test.
 
Had it since new (23 years),yes the problem started suddenly.
Do you think its a fuel problem ?
One small fuel line replaced to bottom carb ,this line I think was leaking air.
 
By cut out I mean the motor stalls,
The RPM at idle is 2000 RMM
Have spark on all plugs
Have not altered the sync link
 
It is easy to accidentally undo the carburetor linkage(especially when replacing a fuel line) when working on this particular motor. Check to make sure everything is in place and the carbs are opening and closing properly. Idle speed should be around 850 RPM and at that speed it should be running on the top 2 cylinders only. If the carbs are synched properly, the bottom 2 cylinders will not receive enough fuel to "kick in" until the motor reaches about 1800 RPM.
 
The original poster appears to be reluctant on explaining what may have happened " suddenly " so from 10,000 miles away it is hard to diagnose !
 
The unit has never caused a problem until this started, today I found a fuel line running to the bottom carb had deteriorate and was taking in air.
Have now adjusted the idle to 850rpm.replaced fuel lines.
Will give it a run Tuesday, will advise how it goes.
Thank or all your advise,
 
After replacing the fuel line,have tested in the water but this has not fixed the problem.
I can recall it started after the starter motor jammed on the fly wheel after the nut on top came loose.
Is it possible the problem may be caused by this.(under fly wheel)(tried to start it before I woke up it was jammed )
Cleaned carbs ,replaced fuel line etc
 
thanks everyone for your help, the problem was solved today it turned out to be a faulty trigger under the fly wheel.
 
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