Rotten core in swim deck----need suggestions

[Halfhitch]

I was seeing lots of crevis corrosion where the ladder bolts through the platform. When I removed the ladder to clean the rusty area, it was obvious that there was wet, rotten wood around the drilled hole. I could push an ice pick sideways far into the core with little resistance.

I started out by removing a small piece of the bottom skin in hopes that I could just pour a small area full of epoxy and redrill. As you can see, that was wishful thinking.

Then I drilled multiple holes with a 1/4 inch bit, searching for the limits of the rot.

It was apparent that it was quite extensive so I decided the remove the complete bottom skin in that section of the platform.

Do you think I should remove just the black rotted wood and replace similar wood blocks before reskinning or remove all the wood in that section and replace it all?

When I do re skin the thing, would it be OK to just use the skin I peeled off and just wet it good, wet the replacement wood and weight the original skin back on rather than go through placing multiple layers of cloth and resin? I've never re cored something like this so it's gonna be a challenge for me I'm afraid. I was wondering also if it would be acceptable to use a single, cut to shape piece of something like Coosa board if it is available in the correct thickness? I know rigidity is my main concern in that area.
Any thoughts would be welcome.

 

[DennisG01]

I think it's your call on whether or not you want to replace the good stuff. I mean, if it's good it's good, you know? That said, it's really not that much more trouble to replace it all. You don't necessarily need to cut tiny little blocks. You can use just a couple pieces of plywood (marine ply, ideally... but NOT PT). Drill a few 1/2" holes in the plywood to help make sure you don't get any trapped air bubbles.

YES, you can absolutely reuse the skin. Lay a single layer of very lightweight glass between the wood and the skin.

You'll want to grind both side of your cut so you can lay a strip of glass there, otherwise you may get a crack showing up at some point.

 

[Halfhitch]

Thanks Dennis.

 

[DennisG01]

If you have an oscillating tool, that will make quick work of removing any of the wood that is still sticking to one side or the other of the glass.

If you don't have one of those tools... now you have a "legitimate" reason to buy a new tool!

EDIT: Just noticed in your pic that you already have one!

 

[Halfhitch]

I finished the project awhile back and the boat is back in business.

Searching for the extent of the rot...

This is what I wound up removing......

Finished....