1997 115 Mercury Rough Idle

djl1006

Recruit
Joined
Jun 1, 2010
Messages
1
I just bought this boat took it to a dealer to be checked out. They rebuilt the carbs. They also told me that this particular year idled rough because it idles on 2 carbs then kicks to 4 when you accelerate. When i get it to the lake i can hear a beeping noise coming from undwer the console. Looked under neith and found the previous owner had wrapped a rag around the beeper so you could barely here it. The boat idles very rough and chugs and shakes like crazy untill you hit some RPM. Try and stop and put it in reverse and it dies most of the time. Surly this isn't normal for it to idle this rough it shakes the whole boat when your trying to troll. I would appreciate any advice. Of course iv'e got it at the lake in a slip 25' pontoon, or i would just drag it back to the marine dealer that checked it out.
 

Sides

Cadet
Joined
Apr 9, 2010
Messages
8
Re: 1997 115 Mercury Rough Idle

I have this exact same problem on a 1995 115 HP mercury. I can't offer any advice, since mine still does it after having carbs rebuilt, new fuel pump diaphram, new plugs.

Would love to hear what others may advise.
 

pigeon laker

Seaman Apprentice
Joined
Jun 19, 2008
Messages
47
Re: 1997 115 Mercury Rough Idle

I have the same motor,except it is a 2000.Mine shook alot and was a bit low on power.I rebuilt the carbs - no help,fuel pump - no help.Brought it to a mechanic - said nothing is wrong,compression good,spark and fuel were good.I read on this forum about replacing the exhaust divider plate gaskets and what do you know - the power was back,but still idled bad.I increased the idle mixture on the top 2 carbs about 1 turn over spec and voila runs great now.Now I have to reprop since I am now over revving it.
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: 1997 115 Mercury Rough Idle

A warning buzzer needs to be checked out immediately to prevent engine damage either from a lack of oil or overheating.

Rapid beeping is an oil problem, a continuous tone is an overheat.

If a rapid beeping with the key ON and the motor NOT started may be a faulty float in the oil tank. They had a nasty habit of an adhesive failure holding the magnetic ring to the bottom of the float, the ring falls of onto the switch and the system 'thinks' you are low or out of oil.

Unplug the blue wires coming out of the switch under the oil tank, if this stops the alarm then order a new tank assy as the float is not repairable.

If this does NOT solve the problem of an oil alarm then add oil to your fuel mix at a 50:1 ratio to be sure you do not cause any damage running your motor while testing to determine your problem.
 
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