I will take the fin off tonight in hopes it works for the weekend. I also checked the foam and it is dry as can me. I drill a little pilot hole under the ski storage and the foam came out dry. Fixed the holes so nothing else can get in there. Any other suggestions other than a new prop?
I've got a '91 Glastron 17ft with a 3.0L. I normally get 35 loaded and with family. If I'm alone, I get about 40 - 42MPH. My Glastron weighs about the same as your boat. I do not have a fin because they are pretty useless on an I/O. I've got a 19 pitch prop too.