Hi--
There may be someone who has a general idea how many were made, but actually "knowing" for certain could only be done by going through many thousands of build records... like a quarter of a million of them... and weeding out the model you are curious about. This might be narrowed a bit if you knew generally when they were made and then only looked at the build records for those years.
Old Town put all its boats into one serial number series, which makes it wonderful for those of us who look up records because there's only one database-- not a separate database for each type of boat. But if you're looking for one type of boat, it means going through records that include everything.
Roger Young suffered some vision problems while working on a project involving looking up the model canoes built by OT... so, searching through the build records can be done... but can be a huge project, with complications! I've periodically looked through OT's records from the 1920s to find Molitor models and have found that in small doses my eyes don't hurt and I don't go bonkers over it.
As for knowing how many are still out there... not many motor boats come to these forums, but maybe a wooden boat oriented forum would have a more accurate guess.
Kathy