Boat seems to be missing 10 mph and 700 rpm

[Striper80]

So I went to the boat yesterday to set the timing. I started out by checking that the throttle blades were opening all the way and I saw that cyl 7 wasn't opening. The set screw was pretty tight nut not tight enough. Not sure how long it's been like this, I checked it last year when I did the link and sync. The linkage was full of slop when I did it.
i wanted to set the timing but it didn't work out. The tide was low and my ramp is extremely slippery at low tide, a lot of trucks have slid in over the years at AHMM. I tried backing down just till the engine was submerged and chocked my truck wheels. I fired it up and let it warm. When I tried to refit up in gear it really bit in and I didn't feel comfortable with how much movement I was getting at 2000rpm so I aborted. Doesn't help that my 4wd only works in auto right now but the boat comes first. Hopefully one of the 2 evinrude shops can get me in this week.