Re: 94 120 Johnson running out of gas
Hi there,
I'm certainly not one of the experts here, but I just got through a similar problem with my 1990 120hp. After ripping apart the entire fuel system on the motor (carbs, pump, hoses, etc,) it ended up being the new primer bulb I installed a few weeks before. My fuel system from the tank to the fuel pump was brand new, but a mechanic friend suggested that I run a direct line straight from the tank to the pump (no filter or primer bulb, which was a little disconcerting but it did entirely eliminate a everything from the tank back-we were concerned that I might have pinched a fuel line when running it through the chase). My motor ran fine once I did that, so I knew it was in that system somewhere. There is possibly an anti-syphon check valve on the tank where the fuel hose attaches that might be hanging up and opening enough to run at low speeds but not enough to give a full flow of fuel. My problem was actually the new Tempo primer bulb that I purchased at West. I got the right size and installed it correctly. It was actually working just the way it was supposed to when you squeezed it, so I had originally ruled it out as a problem. After talking to some folks, I was warned a couple of times that the Tempo bulbs were junky and troublesome and to replace it with an OEM (only $2.00 more at my local marina). I bought the OEM and it solved the problem. To figure out why, I took both of them and blew through them in the direction of the arrow. The OEM was effortless to blow through but the Tempo required much more force to get air to pass. My theory is that the springs that they use in the Tempo to hold the check balls in place are stronger and require more suction from the pump to open them fully to allow enough gas to go through for full throttle (that, and maybe they were hanging up a bit). Maybe some motors have more "suction" power, or possibly my pump is a bit weak, but it certainly was the difference. Unfortunately, it took me two weeks and hours of pulling the fuel system apart to realize it was all in the new bulb.
Hope this helps!
Evan
