Which would you recommend?  Is one or the other product more difficult to work with?  Does one of the products offer a distinct advantage over the other?

Thank you.

Assuming it's a through the hull unit, the last to use is fiberglass resin. It's probably impossible to mix it without hundreds of tiny bubbles which would kill the signal. Use aq high quality epoxy, stirring slowly so as not to fold in air. A round pencil works well, held straight up so it doesn't make air pockets. After sanding the hull very clean with fine sandpaper spread epoxy in a thin layer on both hull and unit base, then rock it onto the hull from one side to the other once to puch out air, then press down firmly. Weigh it down with a sack of rice or sand 24 hours. Some folks make a form around the unit to catch excess epoxy, but that tells me they are gobbing too much on. Be sure the bottom of the unit is flat to a water surface. Some hulls slope, some have a raised rib. The hull exterior outside the unit needs to be smooth and flat there and ahead of it towards the bow. You should first find out what was used to construct the hull at that area as some have a layer of hardwood sandwiched between fiberglass layers, which kills sonar signals.

Jim

Thank you for the info.  I contaced Humminbird tech support and their reply was to use a two-part slow cure epoxy.

I plan to install this new transducer in exactly the same spot/position as the existing one.  The old unit was inside the hull down at the bottom near the bilge pump, and worked well until the transducer kicked the bucket.  I'm going to remove the old one, sand and clean the mounting area, and install the new one in the same location.