How to reseal enclosed transom On An aluminum boat without welding?

If you can remove the cap and pull out the wood, replace it with something like Alaska yellow cedar that won’t rot in the boat’s lifetime. Seal it on all sides with epoxy. Replace the cap with a standard sized piece of aluminum channel - any metal supply place can source it, but typically in 20 ft lengths. Go to a welding or metal fabrication shop and you can probably buy a shorter length of scrap. You could screw the cap down to the wood with countersunk screws, but you’d probably be as well off having a welder skip weld the cap to the existing transom. That’s like a 10 minute job. Or epoxy it down to avoid any leaks.

 

Thousands upon thousands of aluminum boats are built with wood cores and riveted caps. Probably the most common boat here in the midwest.