I'm assuming you mean closing sides of transom in closer towards the single engine, or raising transom notch up higher, or both.
What is it you want to accomplish doing this? Is the transom structurally sound as it is, or does it need work.
Reason I ask is, if transom needs rebuild anyway, you can do a complete rebuild like I did in link below, and when rebuilding make outboard cutout area setting for a single outboard. By the way, a TON of work that I hope never to experience again. If transom is in good structural condition, then anything you add to cover transom notch is kinda going to be "do it yourself" appearing.
http://forums.bateau2.com/viewtopic.php?f=10&t=19949
I used to worry about the large transom notched-out until one time when I was 60-70 miles offshore in my 22' Seafarer. We got caught out there in some severe weather Large waves were stacked up and breaking, some so large they were breaking in front of boat, and landing behind it, but most were coming down on boat and us. Bimini top was crushed and frame ripped out of side mounts, loran and radio antennas snapped in half, and even one of helm seats snapped off with friend in it when one large wave crashed down on us.
Point is, boat cockpit was completely filled with water, and self bailing drains were useless for the amount of water coming in. The only reason we are not still out there was because most of the water that came into the boat was flowing out over the outboard notch like a waterfall and into the ocean. I have absolutely no doubt in my mind, that had we been in a closed transom boat with braket outboard or I/O we would have never made it. So I'm all for the notch out!
Just for the record, all during the previous day up until we lost our radio out there, NOAA was calling for 3footers subsiding to 2s in the afternoon.
Just one mans' opinion. Mike
