Yamaha Outboard Problems

I have a 1990/1995 (not sure of year) Yamaha outboard motor that suddenly started giving me problems. It was running at full speed and suddenly the engine bogged down. I could get it running at about 3/4 speed by having the choke pulled most of the way out. I pulled off the fuel bowl and emptied it and blew out the filter. The boat ran fine for about 1/2 the day with no choke necessary and then started to bog down once again. I emtied the fuel bown and cleaned the filter once again but this time it didn't help. Motor starts easily and idles fine but has no power unless I have the choke pulled almost all the way out. Any ideas before I have to pull the motor and head for a mechanic?

Thanks,

[jb123]

dirty fuel or water, clean / rebuild carbs.