1989 70hp ETLF fuel blowback

I have a 1989 Yamaha 70hp and am getting fuel blowback from the to carb? Any suggestions? I am thinking it is the valves? But seeing as I am back in Iraq now but will be going home soon I wanted to see what I could findout.

Thanks

[boats.net]

Check for bad reed valves.

Will I need to pull the powerhead or can valve replacment be done with powerhead intact

Thanks

[jb123]

pull carbs and intake to expose reeds.hold up to light to see non closing reeds.