Merc 40...... 4hp. Idle trouble

4mercury

Cadet
Joined
May 16, 2011
Messages
8
I just bought this 4 hp. Its in wonderful shape BUTTTTT, when you slow engine down in order to shift into gear it has a very rough miss, or no idle & some times quits. It seems to miss fire & or load up when trying to idle? After running at normal speeds it will idle fine for 15 to 30 seconds then starts this again. Runs well off idle. When I got it I changed lower unit lube, spark plug, gas filter. The owner before changed points, water pump last spring also. Oh yes, one more thing I did notice it seems to be puting some fuel out the exhaust when trying to idle. Starts on second pull almost every time. Where do I need to start looking, Carb, Spark ? Added sea foam to fuel, seem to clear up for a while then started doing the same thing again? Thank You for any help
 

bktheking

Vice Admiral
Joined
Jul 29, 2008
Messages
5,057
Re: Merc 40...... 4hp. Idle trouble

Is this a plastic prop twin 4 hp gnat motor or the old single cylinder metal cowl model?
 

4mercury

Cadet
Joined
May 16, 2011
Messages
8
Re: Merc 40...... 4hp. Idle trouble

It is a single cyl. one piece cowl 1971 model side bowl carb. Thanks
 

4mercury

Cadet
Joined
May 16, 2011
Messages
8
Re: Merc 40...... 4hp. Idle trouble

Oh yea....... Aluminum prop, two blade. serial # 3030273.......
metal cowl
 

4mercury

Cadet
Joined
May 16, 2011
Messages
8
Re: Merc 40...... 4hp. Idle trouble

1971 single cyl, one piece metal cowl, aluminum two blade prop, serial # 3030273, .........NOT a gnat
 

bktheking

Vice Admiral
Joined
Jul 29, 2008
Messages
5,057
Re: Merc 40...... 4hp. Idle trouble

I'd look at cleaning the carb for starters.
 
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