1966 Johnson 20 HP bogging down

[ckdfire]

Hello, I have a 1966 Johnson 20hp motor that is pushing a light 14ft aluminum. My boat fires and runs fine for 2 to 3 minutes and then starts to die ( as if its not getting enough fuel). In order to keep it running I have to squeeze the primer bulb, but sometimes the bulb is flat, like all the air has been sucked out of it. Im thinking that the fuel line and connections need to be replaced, but when I disconnect the line from the engine and pump the bulb there doesnt seem to be a leak. Im alos thinking that it might be the fuel pump......any help please?

 

[itstippy]

Re: 1966 Johnson 20 HP bogging down

The bulb going flat like that is a big clue. Your fuel pump is working great - it's sucking the bulb flat. That means there's not enough fuel flow between the bulb and the tank. Do you have the tank vent open? If not you're getting a vacuum built up in the tank as the motor runs and sucks gas from it. Take the cap off the tank and run the motor. If the problem's still there then the filter screen on the fuel line inside the tank is clogged. The fuel line can't provide fuel fast enough to supply the engine, and the bulb gets sucked flat.
Can you borrow a known good fuel tank from a friend and take the boat out for a spin?

 

[rickdb1boat]

Re: 1966 Johnson 20 HP bogging down

Try a different bulb too. The check valve may be defective....

 

[freddyray21]

Re: 1966 Johnson 20 HP bogging down

i'd agree. I've had a bulb go back causing the same problem. new line doesn't cost much.

 

[ckdfire]

Re: 1966 Johnson 20 HP bogging down

So to answer your questions....yes the vent is open on the gas tank. I have not tried to run the motor with the gas cap off yet but I will try next time. I also wanted to let you know that i noticed a small leak comming from the connector that connects the fuel line to the engine. Im not sure if its leaking because I keep pumping the bulb or because it has gone bad.
So im thinking that I will replace the fuel line, connections and the bulb and see if it fixes the problem...if not I will next try a new gas tank.
By the way, the bulb does not go flat every time, just occasionally when im squezzing it often. What do you think?