nothing last forever.
if original, it may very well be time for a compete re-wire of the boat especially since it's been sitting in a marine environment for 15+ years.
Gradys are great boats, but their wiring has been sub par in many ways. The lack of use of proper marine grade wire and connectors eventually lead to problems due to corrosion in connectors and the wire.
use marine grade tinned stranded wire, tinned marine connectors, waterproof connections with heat shrink or similar, and use some Corrosion X as your friend.
you can try to replace just the block (i like Blue Seas blocks), but when you replace some connectors you may find ugly black corrosion having crept up the wire.
As a rookie years ago i wired my downriggers using heavy extension cord wire from Home Depot and i replaced that wire after just 2 years. That boat sat on a trailer in-land and was used relatively sparsely over the short season yet ugly black corrosion had crept up the wire (non-tinned copper) an amazing 4-7 feet from the ends!
I recently ran 2 pair of primary wires to feed 2 new blocks from the batteries and went a little overkill with 8 ga wire (got a great deal on the spools!).
The heavy wire allow me to add to the block with out worrying about over heating wires and stressing gear (yes, buy a block with more space than you need for eventual additions).
check out genuine dealz for marine wire and connectors, blocks, etc., great prices and service.
Probably not the answer you wanted, but if you re-wire now, you'll avoid a ton of future elec issues which are difficult to trouble shoot and hit at the worst of times and you'll have peace of mind of the next 10+ years.
