Mercury with bad idle

[nimmor]

I have a 1979 40 HP Mercury that is real rough at idle. It is worse when it is in gear. It is not real hard to start except when it is cold. It levels out and runs better at half throttle and seems to run perfect at WOT. I was looing in the manual and came across some info on a low-speed coil and how to test it. I will need to get a digital ohmmeter to get the acurate readings but does this sound like I am going down the right path or should I look at something else? he carburator was the first thing that I thought of but it runs really good at WOT I just don't think that is it.

 

[87merc150]

Re: Mercury with bad idle

I had this same problem. I went through everything and ended up finding a pin hole in one the the lines that goes to the carbs. I found it by pumping up the bulb real hard and then the gas sprayed out of the line very small and hard to see so look real hard. After I put a new gas line in it has idled and ran slow great every since.

 

[Robertbob49]

Re: Mercury with bad idle

I have a 2005 50 hp mercury outboard that has low idle and stall problems. Is there a low idle adjustment? I do not have a manual. Thanks for any help/advice.

 

[FoolOfAFisherman]

Re: Mercury with bad idle

Yes there is a idle mixture adjustment in the carbs. My philosophy is that A service manual is a boaters best friend.