1975 Merc 7.5hp needs cylinders primed to start cold

[Rickus]

I just bought this motor and tried to start by choking, not choking, pumping the primer bulb and would not start. I checked the spark and it looked fine so I put a few drops of fuel mixture directly into each cylinder and it started first pull, and every first pull thereafter while it was warm. Trying it again after it cooled off, same problem, pulled rope repeatedly, tried choking again, nothing. But priming the cylinders seems to work and it runs fine after that and starts fine after that until it cools off again. Does that sound like a fuel pump problem? Carb needle sticking? I have basic knowledge of gasoline engines but never worked on an outboard before so I need really simple terminology and instructions. Thanks for any ideas you might offer.

 

[Silvertip]

Re: 1975 Merc 7.5hp needs cylinders primed to start cold

Make sure the choke plates are closing fully. They worked when new, and should work now. If the engine has a primer system, make sure the primer is working properly.

 

[Rickus]

Re: 1975 Merc 7.5hp needs cylinders primed to start cold

Thanks, I noticed that the choke plate does not close all the way but wasn't sure if it was supposed to. If I pull the choke all the way out, it closes completely, but the spring pushes it back open about 1/5 of the way when I turn loose of the choke knob. There is no filter or anything except a plastic grid cover over the carb intake. Is that normal?

I don't see any primer system except the fuel line bulb. I'll try to adjust the choke to close completely and see if that helps. Thanks again. I'll post the result of this experiment.

 

[Rickus]

Re: 1975 Merc 7.5hp needs cylinders primed to start cold

I tried to find a way to adjust the choke, but could not see any way to shorten the pull distance of the choke cable so it stays shut. I held the choke knob closed with one hand while pulling the start rope with the other. Some gas ran out of the carb during that exercise and the motor actually started after several pulls without priming the cylinders this time, so I assume that the choke is the problem. I'll let it cool down and try this process one more time to see if it starts the same way again. If that choke is indeed the problem, then I will need someone's advice about how to shorten the cable I guess. The cable has a little ball on the end of it that hooks into the lever on the carb, but I can't see how to reattach it if I cut it off. Also like to know if where to find a post about adjusting the carb idle in addition to the choke adjustment because it does not idle well in the "shift" position which is the slowest of the three positions on the throttle--"shift", "start", "fast." There are two screws in the front of the carb--one horizontal screw with a spring on it and another on top near where the point of the first screw would be inside the carb. Which one does what? And do they both require adjusting together?