Has anyone tried to use nylon or Teflon squares in three places (every 120 degrees) around the shaft to take up the play?
Absolutely not. If you've ever looked at the inside of a cutlass bearing, it is a rubber liner with grooves cut in it for cooling. It presents a large bearing surface as compared to the three squares of plastic you intend to insert. But a
FAR greater problem is how to attach the pieces of plastic to the brass bearing casing. Neither teflon or nylon take to glue.
I can see one hell of a pile of damage when when that mess you install fails. And you're willing to risk your 37 ft. C&C to this idea ?
Seeing as how that idea was so bad, I'm going to suggest that there is a way to do the job without removing the engine or the shaft. One of the ideas was produced by
@Tally Ho in an excellent video in one of his postings.