Johnson 20 troubles

Having problems getting all the power out of my motor. She revs fine and has power out of the water, but when under load I am getting no where near the top end I use to get. I thought it might be the dreaded ethenol problems so i took apart the carb the other night. Everything looked good, so I did a compression testand found 120 on both cylinders. I am stumped to what might be causing the power loss. I did find one plug that had a little wet fouling on it. COuld this cause a drastic loss in power? It is almost like I added 500lbs to the boat, but nothing like that has changed.

What is the condition of the prop? It might be that the prop is out of true or have excessive dings that might be limiting your top end. What about the bottom of the boat that it is powering. Fouled or roughed bottom may also be contributing.