Is it possible to fix unglued transom of inflatable boat without expensive repairs?
Yes, it is possible to fix unglued transom of inflatable boat relatively easy. First, try to glue what you can back. Glue transom holder back to transom sides. Do all repairs in low humidity environment. Wipe with Acetone 3 times, wait 5 minutes between applications. Then apply PVC boat glue 3 times with an acid brush. Wait 5 minutes between first 2 application and 5-10 after last application.
Join glued pieces together and press with old spoon to remove any air bubbles. Then get stainless steel screws with large stainless steel washers and screw directly into transom holders every 2-3" on both sides of transom holder. Screws will hold transom pretty good, even better than glue. As long as transom holder is glued good to the boat tubes, you can still use boat after transom repairs for many years.