2002 340, soft area around small hatch

[speakrdude]

I was affraid this may happen and sure enough.
An area around the small starboard hatch on the top of the boat is getting soft. I figured out how to tell pretty well with the boat out in the hot sun and using your bare heel to test.
So here’s the question.
I reallly really really do not want to cut the exterior fiberglass, esp with the anti-slip pattern and I really dont want to remove the interior either.
I’ve done this repair before on a 88 model 300, using a paddle bit and a drill to mulch the soft wood, then replaced with thickened—resin and plywood where-ever we could fit.
We made this repair from removing the hatch.
Any other ideas? Better ways to remove the soft balsa?

 

[Strecker25]

Inside would definitely be best, but I get not wanting to take down the headliner.

The issue with the drill is the reach, probably depends on how far the rot goes whether you can get it and being absolutely sure you’ve removed it all would be tough. I could see it being really difficult to seal the edge of the “good” core where it mates to the new stuff and then getting the new core to adhere to both sides of the glass shell.

 

[Lazy Daze]

I think it's well worth it to try and ream out the soft wood by removing the hatch. Removing the hatch is easy, so you might as well try that way first. You might have to start with a cut-down paddle bit if you can't the bit/drill into the opening. You also could start with an allen wrench in your drill, if it's easier.

The one thing I'll say is that "most" times, there is more soft wood than you expect. But if you can get most of it, I think you'll be alright. You can use a platic baggie like a cake decorators bag to squeeze some (first) unthickened epoxy deep into the hole to help saturate what is there. Then come back with some thickened epoxy and squeeze it in there. Then stick in your pieces of plywood or end grain balsa or coosa or whatever. The plywood does NOT have to be one piece. However, I WOULD pre-saturate your pre-cut plywood pieces - which means applying epoxy to all six sides a number of times over the course of about 30 minutes. This ensures the epoxy is thoroughly soaked into it and you'll end up with a much better bond.

Don't run the core all the way to the edge/perimiter of the hole. Stop about 1/4" short and then come back and fill with thickened epoxy. If water gets past your hatch seal again, it will never soak into the core again.