Here's the final story on this. I decided not to try to use the old
transducers; they were very old, corroded, and the wires were brittle
and breaking.

The old depth thruhull came out easy enough. It was a 1-inch diameter
hole, and the new thruhull needs a 2-inch hole. Two drills gave their
lifes to complete this operation. The old speed transducer was a bitch
to get out - the whole assembly would turn when i tried to back off the
old nut. We had to hammer in a big knive (think crocodile dundee) into
the transducer so it could be held to allow the nut to be removed.

I used 3m 5200 fast set as bedding sealant. And I know some would be
against this, but I never plan to remove these items again!

And I like my new ST40 bidata a lot.

buddy