[sbw1]

Don't know about your isolator. Do have experience with the transom door question. We bought our 3200 open new in 2004. It was sitting in the water in the showroom in Harbor Springs. The seal was damaged when someone looking at the boat damaged the seal by shutting the door without returning the locking handle to the proper position. The dealer removed, the old material and cut a length of new material from a spool of it in their parts department. I would say go to a full service marina and buy the length that you require. It is commonly used on boats. I have seen spools of the material you are talking about at our storage marina as well. Never have I seen it sold in a hardware store.