Today I borrowed a freind's 1970ish 6hp Johnson. He said he had a bit of trouble with it this spring so he cleaned the carb, put new spark plugs in, and changed the fuel line. He had it out the other day and said it was running great, he even called me so I could hear it. So I tried it today and it kept dying on me. I tried different lean/rich settings, and also ran it idled and wide open. None of which made a difference.

Just before it would die the rpms would go up. Sometimes if I throttled down I could keep it going. I could usually get it going after I choked and primed it. I did have to mix up some gas before I hit the water and I am wondering if I did something wrong. I mixed it 50:1, 3oz of oil per gallong of gas as stated by the instructions on the oil.

One reason I think it is me is that I had a 1962 sea king I was trying to fix up and it was doing the same thing.

Help!

Does it have the fuel tank on the engine? If it does, did you forget to loosen the vent screw?

It is typical for an outboard of those eras to rev up just before they stall from lack of fuel.

If, it has a separate tank, is there a vent on the tank that you forgot to loosen?

Evinrudes and Johnsons (they were the same motors with different badging) originally had a double fuel line, and a pressurized tank. Sometime in the 60s, if memory serves they went to a single line fuel tank. If you have a double line, and you didn't tighten the fuel filler cap, you can pump the fuel to the engine ,manually, filling the carb, but it will run out since the tank cannot build pressure.

If a single line has a leak it will suck air and run out of fuel. Could also be a faulty fuel pump since you could prime it and get it going.

If a single line has a leak it will suck air and run out of fuel. Could also be a faulty fuel pump since you could prime it and get it going.

My friend looked at it and that sounds like the problem. Every time I started it the primer bulb was empty. After further inspection he found the hose was leaking where it attaches to the tank. Phew.. simple thing to fix.