I recently purchased a 1980 O'Day 23 with a non functional depth finder. I am looking to replace the depth finder and need to decide on a transducer for it. The boat has an ancient thru hull P-19 transducer that so far as I can tell is non functional or obsolete. My marina is willing to swap it out for the cost of labor (don't know how many hours?), but I am reluctant to reopen a hole in the bottom of the boat (the boat is currently amazingly water tight, rarely ever have to pump the bilge). So I am considering saving the cost of labor and installing an in hull transducer instead. Can folks tell me their experience with in hull transducers? Also, Garmin says that the P79 will work on a solid fiberglass hull up to 5/8ths inch thick. Can anyone tell me the thickness of the hull of a 1980 O'Day 23? I was planning to install it near the centerline in front of the keel. Thanks