Johnson 15 Hp outboard fuel issue? please help

My grandfather and I went out on the river yesterday with his 14ft johnboat. He has a Johnson outboard motor that is a 15 hp. the model number is J15RSUA.
Ok. so when we primed the fuel up from the external tank we started the motor with the choke full. It ran, bogged down and cut off. We tried various attempts to get the motor to run and finally were able to constantly pump the primer and the engine would stay on....but not long. I'm trying to figure out if there is a leak somewhere in the lines or if the fuel pump isn't working properly. It may be a carbuerator issue but im not sure. If anyone can help that would be awesome.
thanks.

Re: Johnson 15 Hp outboard fuel issue? please help

If it will run as long as you are pumping the primer bulb, chances are good that the fuel pump is the problem. You are correct in checking the fuel lines for leaks, loose clamps etc. Also make sure the fuel tank is venting and the fuel is fresh.

Re: Johnson 15 Hp outboard fuel issue? please help

Fuel pumps are tricky, and the diaphragm will usually go out if the vent is not open while the motor is running. One is enough to need replacement, yep, only one time running with a closed vent will do it. Next time out the motor will idle but no mid to top end. Another thing I ran into recently is fuel line air leaks in the bulb itself, or connections, or lines inside the motor cowling too. Check all connections with care, and replace them as needed, they don't last forever. Might check plug color and wetness, that you probably did that first, to see if you need any help there too.

Probably fuel pump diaphragm though, try a replacement kit from iBoats, and/or new one so you have a spare on board.

Good Luck, Cal

Re: Johnson 15 Hp outboard fuel issue? please help

thanks guys. I do remember that there was a little gas that was spurting out from the connection to the fuel tank. That connection should be sealed tight when you connect it correct? I hope that it's just the connections and not anything serious that's gonna wipe a weekend off the fun calendar.