1998 Yamaha 25 hp

[jr.deerslayer]

I currently own a 1998 Yamaha 25 hp 2 stroke. It has been running great until a few days ago when I tried to launch my boat. The engine started great like normal but wouldn't run without the choke. I was able to get to a fishing spot by pushing in the choke when it started to die. On the way home I had to continue to do this until about a half mile from the launch, it started to run perfect. I let it idle for awhile and everything was great. Today I tried to run it on muffs and it still starts great but needs choke to continue running. The primer bulb doesn't stay hard, I pump it until its hard and start the motor it will run great for 20 seconds or so but then will quit unless I catch it with the choke. If I pump the bulb when running it has no effect. The previous owner had it completely gone through and like I said its been running great for awhile now. Thanks for any help, its really appreciated.