Low speed high rpm

My boat sat for about 1 month unused. We couldn't get up to the boat. We finally got out and the boat is running at half speed and really high rpm's. The motor is a 1989 40hp evinrude. It had this problem when we first took the boat out after we purchased it. The problem then was the carb linkage broke off. I pulled both carbs off and rebuilt them. After I fixed that it ran about 20 mph at about 3500 rpm. Currently it is running 10 mph at 4500 rpm. I pulled the carbs off last night and sprayed some carb cleaner through them. When I was doing this I noticed the linkage between carbs was loose. Could the unsynched carbs be the problem or is there something else I should be looking at? The boat is about a 45 minute drive from home.

Prop hub may be spun.