1980's 20hp Mercury fuel/Electrical issues?

[erpau0732]

I bought a 1980's Mercury 20hp and it was a hard start you have the pump the primer bulb frequently while the motor is running or it will stall. It ran well when it was running. I cleaned the carb to try and fix the hard start and it did it starts with 2 or 3 pulls now. But the primer bulb is still and issue it will run out of gas randomly? Also now that I have cleaned the carb if you rev it up to higher Rpms it back fires and misses and smokes? I am stumped because it ran well before the carb clean?

 

[flyingscott]

Sounds like you have a fuel pump problem or the vent on the gas tank isn't open. You will probably need to Rebuild the carb with new gaskets. You should have the fuel pump on the carb so make sure the kit comes with those gaskets and a new primer. Get carb cleaner and spray through all the holes that look like something can go through them. Then use compressed air and blow through them again.

 

[erpau0732]

I rebuilt the carb and just for testing to see I set the mixture to really Rich and it ran better. So I think their is a vacuum leak which is leading to insufficient fuel delivery. But I think I will,buy new gaskets for the carb

 

[erpau0732]

How do I determine where the vacuum leak is on an engine like that? If I buy a pressurized tank do I have to worry about that?

 

[flyingscott]

NEED SERIAL #. Also do a compression test and a spark test. Why do you think the carb was rebuilt if you didn't put new gaskets in. When the carb is off look at the reed valves if possible.

 

[erpau0732]

Is the aluminum freeze plug on the block stamped With the serial #? Because if so I have it and it doesn't match anything I can find its A919053

 

[erpau0732]

I don't have a spark tested but when I grounded the plugs on the block it was good spark. Also compression is 110 and 112

 

[flyingscott]

Your motor is a 1986 model buy the complete carb kit that has all the gaskets you need and the primer assembly. And clean it with carb cleaner and compressed air. I have no idea what you mean by pressure tank. Here is the part# for the kit quicksilver 1395-9761-1 be careful when you open it there are small springs and a bearing in it.

 

[erpau0732]

The primer as in the thing you pull in and out a couple times to start the engine? And thanks that's for all the help. I'm talking about buying a pressurized fuel tank to not need a fuel pump

 

[flyingscott]

You can't put a pressurized tank on that. For one thing nobody has built an outboard with a pressurized tank since the 50s. Buy the kit and you will get the new diaphragms and everything to make it work like new.

 

[erpau0732]

Alright, any ideas as to what the mixture screw should be set at

 

[flyingscott]

1.5 turns from lightly seated to get you started after it is warm you make the final adjustment

 

[erpau0732]

Okay so the setting I bought it at was 2 and 3/4 so It may have been rich

 

[Bill kubiak]

How do I determine where the vacuum leak is on an engine like that? If I buy a pressurized tank do I have to worry about that?

Here is an Old trick but be careful when looking for a vacuum leak. start motor Get out your propane torch, turn it on but do not light it, move it around the carb, when the motor suddenly speeds up, you found your leak