Smoke could be on the right track,Might want to change the fuel pump. Not sure on omc, but pretty easy on a merc. I could tell when mine was failing, after about 15-20 minutes of trolling, I'd hear th motor start to slow down and I could pump the ball to revive it. They'd last bout 2 seasons.

The engine has to be turning over for it to build pressure and the primer to shoot in fuel. You're not gonna get a long squirt hitting the primer just from pumping the bulb up. The fuel pressure will rapidly drop when you push the key in, qnd then theres no more fuel unless you're turning it over for it to pump. And dont go putting a pump on until you check it as they're about $300-400 last I heard.