1994 Johnson 15HP J15RERE

Hello everyone,
I am new here and wanna start off by saying thank you for having me. I have been reading some of your stuff and makes me feel I am in the right spot.
I have just been given a 14ft Arkansas traveler that has a 1994 15HP Johnson outboard. It’s been sitting for roughly 18 years with a cover and under a canopy. The motor looks like it’s only been used a couple of times. My problem is the motor starts up fine and will stay running under throttle, but as soon as I let off it, the motor falls on it’s face.
I have checked for spark (good) I have rebuilt the carburetor (good) I have taken apart the fuel pump (seems to look good) I have taken the fuel cell out of the tank (seems to look good). I have replaced the primer bulb. I don’t know how hard the bulb is supposed to be, but has a little squeeze to it, but firm.
It will start with the choke, but will not stay started long enough for me to push it in. But once I do it starts right up every time. I cannot keep it started by pulling the choke half way out. I’m just kinda of lost at this point and hopefully you guy can help

Anything that's been sitting that long needs A NEW fuel pump
diaphragm. New fuel hose and new impeller. Did you SOAK the
carburetor or shoot carb cleaner thru the carb?

No I have not, but I will. But why a new impeller, like I said it’s like brand new, not even a scratch on the impeller. Also, I don’t think there’s any vent on the fuel tank, unless it’s built into the fuel gauge where I plug the fuel hose into

The impeller is rubber.-----Rubber is not a " permanent " product.-----Rubber deteriorates with time.-------The motor does NOT have an overheat warning buzzer or an overheat shutdown system.------On overheat it would run till it destroys itself !!-----A wise owner would install a fresh new one.--------Just replaced the impeller on a 1990 model recently because the last time I did it was 10 years ago.------Doubt that impeller had more than 100 hours on it.

Your talking about the water pump impeller? I have replaced the while water pump. I will be buying a whole new gas primer bulb fuel line and letting the carb sit in some cleaner over night. Thank you Racerone. I will keep you updated. Also racer do you know what the diaphragm does in the fuel pump, should i buy a whole new fuel pump or the rebuild kit will work? quite of bit of price difference

Pressure operates the fuel pump.------The pressure on the diaphragm compresses the spring and pushes fuel to the carburetor.-----Then the spring pushes the diaphragm back to pull fuel from the tank.-----Replacing just the diaphragm is easy in my opinion.---No kit required.----Others will dispute that.

Very good. I will start with just the rebuild kit and keep this forum posted. Thank you again Racerone. I will tell you tho, when I pulled the fuel pump apart the black diaphragm type gasket looked really good

Then no need to jump all over the pump.------Why not test your motor ?----If operation does NOT improve with operation of the manual pump, the pump on the motor is working just fine.-----If operation of manual pump makes the motor run better then you have issues in your fuel system.