Hello, I have a 1987 Grumman 24’ pontoon that I rebuilt 10 years ago which already had a Johnson 90 outboard and she finally blew up last season. The boat has no tag inside and I am wanting to upgrade to a 115 4stroke which weighs 100lbs more that the 90 that was on the boat. Can anyone share some information to help me out. Can this be done safely? I see some calculators online but I don’t think that I am doing it right. I can’t even figure out what was on the boat originally because of its age. Any help would be greatly appreciated.