Merc 120 2.5 rough at idle and up etc.

[trepka2001]

was running good then i started having problems with rough running @ idle and cuts out when i try to accelerate. i have to keep pulling back on the throttle to prevent a stall but will eventually get it up to full throttle without any cut out at full. as i back it down it will start to rough idle again, i'm thinking fuel filter or bad gas??

also, don't know if this matters but i have always had a blocked fill vent tube but it has never caused any problems before.

 

[Don S]

Re: Merc 120 2.5 rough at idle and up etc.

How long since a full tuneup? Hows the plug wires. Have you done a compression test lately?
Do you have a water seperating fuel filter (you should) any water in the tank, fuel system, or carb?

 

[trepka2001]

Re: Merc 120 2.5 rough at idle and up etc.

just bought the boat in July but (i know this doesn't matter) but everything looks in great shape. i was going to replace the fuel filter and put in new plugs, maybe they're fouled but ruled that out because of smooth running at 3/4 to full throttle????

 

[trepka2001]

Re: Merc 120 2.5 rough at idle and up etc.

bhj

 

[Don S]

Re: Merc 120 2.5 rough at idle and up etc.

bhj

 

[JustJason]

Re: Merc 120 2.5 rough at idle and up etc.

maybe they're fouled but ruled that out because of smooth running at 3/4 to full throttle????

nahhh... they still could be fouled. they could be recieving more voltage when the motor is a wot, and not so much at idle.

start with a full tune up. All filters, plugs, points if its got them. If it's the carter fuel pump don't forget about the filter in the pump itself.

 

[trepka2001]

Re: Merc 120 2.5 rough at idle and up etc.

thanks for the help!! i'm in the process of a full tune up, want to get it in the water one more time before the water turns to a solid ice block!!!