1975 Evinrude 6HP fisherman Carb issue

RyanK128

Recruit
Joined
Jun 21, 2017
Messages
2
Hi, I'm having what I think is a Carb issue with my 1975 6hp outboard. first started at full throttle where the motor would lose power then re-gain it intermittently. I have since removed the carb and lower bowl and tried to clean it. used compressed Air to blow through inlets. Put it back on and fired it up ran great for 15 Mins at low speed while I adjusted the low speed mix.Then when tried to open up the throttle and rpm went up a bit and it started to smoke heavy (more than normal) started to stall when a tried to reduce the throttle. The only way I got it to run nice in this state was to shoot some compressed air in the carb? any advice?
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,046
Does the spark jump a gap of 1/4" or more , yes or no ?------These motors have a history of the coils cracking with time.-------If it does not have a set of replacement coils then it needs a set.
 

RyanK128

Recruit
Joined
Jun 21, 2017
Messages
2
Coils & plug wires were replaced in 2004, will check on the spark gap and get back to you.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
Sounds like the fuel pump diaphragm may have ruptured. Remove the pump from the motor (hoses attached), and give the primer bulb a squeeze. If gas squirts out the hole in the backside of the pump, the diaphragm is ruptured.
 

OptsyEagle

Lieutenant
Joined
Sep 13, 2006
Messages
1,356
I would do a cylinder drop test. Sounds like it is running on one cylinder, intermittently. It will idle unnoticeably on one cylinder but will have no power at the top end of throttle. If the cylinder is cutting in and out you will get the symptoms you describe.

The drop test is easy. Start it up and let it warm up. At a fast idle and with a pair of insulated pliers pull off one spark plug boot at a time. The motor should be able to run on only one cylinder so if it dies you know the other cylinder was not firing or was very week.

If it is intermittent it makes it much harder as does any intermittent problem. Intermittent cylinder drop can come from a spark plug almost fouling or a point almost corroded and I am sure a few other things. With the spark plug and point issue, intermittent usually becomes continuously fairly soon so run the drop test to see how the motor is really running.
 
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