Here's the reply I received from my insurance company:

A review of your declarations page does, indeed, indicate that your Yacht Policy does not include Coverage F for Personal Effects. However, the E790 Angler Endorsement to your policy does provide up to $5,000 of coverage for Fishing Equipment, which is specifically limited to rods, reels, tackle containers (including items stored in the container such as artificial lures), electric trolling motor, and other fishing-specific items. More than likely, the loss of the GPS would be something that a homeowner’s (or tenant's) insurance policy would cover, even if lost or damaged aboard your boat. So, I see no issue with retrieving what remains of the GPS when permissible and safe to do so and having you secure that.

So while we don't have personal Effects coverage, we do have a rider (whatever an E790 Angler Endorsment actually means) which covers angling related items but not items of a personal nature.

Just FYI to anyone reading this thread. The reason my representative replied about the GPS is we have all our way point information in it. Annually we remove the navionics chips but I don't think they have our way points on that chip, believe they reside in the unit itself. If so we might have lost all our numbers over the last 30 or more years which sucks. Always intended to write them down in a log and never did. Trying to see if I can get the unit which I'm sure was destroyed and see if someone can retrieve the information. Don't make the same mistake we made, those numbers are gold and irreplaceable and if lost would hurt.