Restoring my 1976 Tri-hull, deck flexing question

[Dot's Yot]

Hi folks! I'm doing a fairly significant restoration on my 1976 tri-hull, and I've just about finished prepping it for new paint (more on that in a different post, if anybody is interested). Now that I have it all stripped down, I'm noticing a couple large areas, about 18"x18" where the deck flexes ever so slightly. About 1/8" to 1/4" max deflection if you push down in the center of one of the 18x18 areas, and you have to push pretty hard or walk on it to get it to flex. I know there's doing it right, and doing it good enough, and I've pretty much convinced myself that I only need to do it good enough, and not rip out the entire deck... for a number of reasons: This boat hasn't seen water and has been in a garage, untouched, for the last 12 years. Prior to that, it was only on the water about a dozen times a year. It was born and raised in Colorado, where it's usually about 8% humidity. It really doesn't seem like a problem with rot, where it's going to get worse over time, but I'm not sure. The spots are also under where the back-to-back seats mount, so it's not like you'll ever be walking on these areas.

My question is should I do anything at all, or would it hurt to put down a 4x8 sheet of 1/2" marine plywood and fiberglass it in? Other than the downside of some extra weight, I'm leaning towards going this route just to make it all flat, hard, and sturdy before I recarpet. If I'm just burying whatever problems lurk underneath for the next sucker who decides to restore this boat, I'm good with that, as long as it lasts another 42 years. I also don't live in a lake house, so I'll realistically be using this boat summers only, a couple weekends a month, and never left overnight on the water.

Thoughts? Am I committing a huge sin by not ripping out the deck and the marine gods are going to strike me down? I have a short video that I just posted on some FB groups, not sure if this link will work:
https://www.facebook.com/sam.veucasovic/videos/10100419950798238/

 

[Scott Danforth]

Am I committing a huge sin by not ripping out the deck and the marine gods are going to strike me down?

Yes

your attempting to put lipstick on a turd..... prior to making it pretty with paint, you need to make it safe with a hull restoration

the last thing to rot is the floor.

your 44 year old boat will need new stringers, transom and floor prior to you ever worrying about paint.

dont even attempt a band-aid fix with the deck over. thats just bad form.

 

[Dot's Yot]

That's what I was afraid of, but I get it. I'm still going to be painting it first, and will just protect the paint while I'm working on the floor.

I drilled out a big area with a hole saw and the plywood is indeed turning to dust. But the stringers seem rock solid, and the transom feels like it's made of lead. Maybe I'll get lucky with just a floor replacement once I tear into it.