90hp bogs down at full throttle

by jon howell
(acworth, ga)

I have a 1983 Johnson 90hp. It ran great about a month ago. I took it out today and it cranked and idled fine. Even when throttled at low speed it was fine but in full throttle it bogged down and would never get on plane. The gas had been sitting in the tank for a month but I don't think that would be the cause. Any suggestions?

Jon