I'm about to order my first new pontoon. A few years ago, I co-owned a used Sylvan 24ft. with a 90HP Mercury. I'm ordering a 21SLX with 2 25" tubes. I hope to cruise, water ski, and tube, often with 4-6 adults on board. Should I go with a Yamaha F90LB 4 stroke or upgrade to a 115HP?