The only way to be 100% sure is to drill small exploratory holes from the inside . If the shavings are dark, wet, or smell like mulch, the core is gone. 🏗️ Repair Options: Wood vs. Composite
Remove the outboard, trim tabs, scuppers, and the aluminum transom cap.
Use a plastic mallet to tap across the transom. A sharp "ping" is good; a dull, hollow "thud" indicates delamination or wet wood. grady-white-transom-repair
Chisel out the rotten wood. On older Gradys, this often turns into "mud".
Butter the new core with thickened epoxy or polyester resin, clamp it into place, and glass over it with layers of 1708 Biaxial Cloth . The only way to be 100% sure is
While every model (from an Adventure 208 to a Sailfish 252) differs slightly, the professional "outside-in" method is common for DIYers:
Grind the inner skin down to fresh fiberglass to ensure a mechanical bond. Composite Remove the outboard, trim tabs, scuppers, and
Use a multi-tool or circular saw to cut away the outer fiberglass skin . Carefully pry it off to reuse later if possible.