Sorry to hear about your injury. I have used three sizes of trailer tires. I used 8 or 10 inch wheels/tires (can't remember which) for about 8 years hauling my pram all over the place. I went freeway speeds while towing it all the time. I loaded it down with hundreds of pounds of camping/fishing gear. I always carried a spare and used it about once a year. I used it hard and it never let me down. That being said, if I were to do it over, I would get bigger ones. The cattle guards were tough on that particular size. I did sell it to upgrade my trailer and decided to put 13 inch wheels on my new trailer, which seems perfect. I had a trailer with 15 inch wheels for one of my boats and which turned out to be much more than I ever needed. For a 100 lb pontoon boat, 12, 13, or 14 inch wheels should be just fine for you.