1975 mercury 20 hp 200

[mek07c]

Just bought a mercury 20 hp 200 serial number 4106849. It didn't want to start so I rebuilt the carburetor and installed new spark plugs. I checked to make sure that the plugs were firing. After third pull it cranked right up and ran great for like 20 minutes. I came back two hours later and it will not crank now. I notice that after attempting to start the motor, there is gas coming out of the throttle plate hole. Is this normal? Any suggestions on fixing this problem.

 

[The-Machinist]

Re: 1975 mercury 20 hp 200

Sounds like your float is sticking. Sorry to say, but it sounds like you are gonna have to pull the carb again. Are you running any kind of fuel filter?

 

[mek07c]

Re: 1975 mercury 20 hp 200

I noticed that when I bought the rebuild kit today it didn't come with a new float so I replaced it with the old one. Could this be my problem?

 

[The-Machinist]

Re: 1975 mercury 20 hp 200

Its more likely you have a small dirt particle in the seat area, or the float level is set too high. A fuel logged float should have been pretty obvious. Brass or plastic float?

 

[mek07c]

Re: 1975 mercury 20 hp 200

The float looks like an old cork float. Is the seat that you are referring to where the needle is pushed up by the float to stop the fuel flow? I did notice that when I primed the bulb it did not get stiff. How do I adjust the float level? Do I simply bend it a little more down or up?

 

[The-Machinist]

Re: 1975 mercury 20 hp 200

First off I would buy a good service manual for your motor. It will contain all the info needed for float adjutsments. Second, I would order a new (plastic) float, as a 35 year old cork float is bound to have some fuel logging issues. I have had bad luck with the varnish coating becoming brittle and flaking off too. The float is the first place I would look at. I have 3 of these motors, and they are rock solid little workhorses. Once you replace the float and get it set at the proper hight, it should purr like a kitten all day long. Just make sure you hav some sort of fuel filter before the fuel pump. I use a clear inline disposable filter from wally world, the clear housing lets me look for water in my fuel, the FIRST thing I check if im having running issues. Hope this helps.