Welcome to Harbor Models Inc.
Made from hard polymer
Triangular piece is 5-3/4" long. Will fit up to a 3/8" diameter stuffing box.
Shape the triangular piece to the profile of your hull with some sanding and run the stuffing box through the two pieces. Glue/epoxy them together for a watertight, strong finish. From inside the hull put two small screws through the bottom into the shaft support and glue/epoxy around the holes.
Depending on the contour of your hull the finish product should look something like this: