Amateur needs advice

[Lubird]

Hi, folks. I own a storage business and a customer signed the title of a 1978 Thundercraft Magnum SS over to me in 2016. It sat in my garage until recently. I've had the motor rebuilt, now I'm into the cosmetics. At some point, the back to back seats were removed and four pedestal fishing boat seats were bolted to blocks glued to the floor. I needed to remove the carpet to remove the blocks. I've found that there is no plywood floor. I'm right down to the fiberglass.

Was there ever a deck? Was the carpet always glued to the fiberglass? Photo three, left side, shows two of the "blocks" that two seats were bolted to. Neighbor thinks they are fiberglass and added. The other two were wood and glued to the fiberglass floor.

The only back to back replacement seats I find are all made by Wise and have a plastic box for a base that is bolted into the floor. Can i bolt them to the fiberglass? It's not flat, it scoops down on the sides.

Photos 1 and 2 are before I took out the seats and carpet. Photo 3 is a photo of the floor. The white rectangular marks appear to be where the original seats were. I'm really stumped. Any info or advice would be appreciated.

 

[Baylinerchuck]

Are you sure that’s not fiberglass covered plywood? Boats of that era are mostly wood core encapsulated by fiberglass.

The plastic bases could be trimmed to fit the exact contour of the floor. Yes they can be bolted to the floor. All penetrations should be properly sealed so water doesn’t get under the deck into the flotation foam.

 

[Lubird]

Thanks so much, Chuck. I talked to my brother and he mentioned fiberglass over wood. This is so helpful, I was afaid I'd have to install a plywood floor. But he said I'm better off with the fiberglass, I can just recarpet. I'm also glad to hear that I can bolt into the floor.
Any suggestions on how i would seal the bolts into the floor?

 

[Lubird]

Just thought I'd post an update. My neighbor was right, and the blocks in the back were wood blocks covered in fiberglass. I got them out with a hammer and prybar. Before and after photos.

 

[gm280]

If I were doing this, I would remove ALL the wood and rebuild it back with fresh rot-free wood, sealed with fiberglass and polyester resins. Then you can make whatever type seat bases you like and even polyester them to the subfloor. But that is just me.

 

[Lubird]

Hi, I've found that my floor is wood encapsulated in fiberglass. There is no wood, that is what confused me. Or at least it doesn't look like wood.

 

[Baylinerchuck]

Hi, I've found that my floor is wood encapsulated in fiberglass. There is no wood, that is what confused me. Or at least it doesn't look like wood.

The plywood is the core material in most boats of this era. Once the wood is laid, several layers of fiberglass are laid over top.
Seal holes with 3M 5200. Don’t use silicone.

 

[jbcurt00]

Hi, I've found that my floor is wood encapsulated in fiberglass. There is no wood, that is what confused me. Or at least it doesn't look like wood.

The floor is wood, but there is no wood?

Seems contradictory....

 

[Baylinerchuck]

The floor is wood, but there is no wood?

Seems contradictory....

I’m guessing that what Lubird is saying is that the wood wasn’t exposed and therefore couldn’t be seen. Those who are new to boats, or haven’t rebuilt one probably think they’re all fiberglass.

 

[Lubird]

I’m guessing that what Lubird is saying is that the wood wasn’t exposed and therefore couldn’t be seen. Those who are new to boats, or haven’t rebuilt one probably think they’re all fiberglass.

I was expecting to see a plywood floor. When I only saw fiberglass, I was wondering if it was supposed to have a plywood floor over it, but I've learned that it actually is the floor. I can see where the original seats were attached