Fastening Pedestal Seats in '74 Tsunami?

[Handful in NC]

What's the best way to fasten new pedestal seats securely to the deck on a Sceptre/Tsunami? I'd rather avoid toggle bolts or screws.

I was planning to put an access hole in the center of the pedestal circle, large enough to reach through to place T nuts on the underside, but it looks like I'd be going into a foam filled box.

This image was pulled from another Forum member, and I assume is the same construction as my boat.

[htillman]

I installed very tall pedestals and used screws and 5200 and had no problems. There is no way to really access under the deck.

[krisis7]

fabricate a plate on the underside of the deck before reinstalling, then you can fasten securely.

[abl1111]

My floor was solid so I used screws and 5200 ( just on mated surfaces ) as well with tall pedestals - not problem. SOLID !

However, a 250 lb guy in a rolling sea, I'm sure would rip that sucker right off.

If your deck is off - make a plate. If it isn't, then I'd use the heavy-duty screws and 5200.

Anyone know how thick the area is under the pedestal that the screws get screwed into ( after removing the nonskid/deck ) ?

[htillman]

In my opinion in a really rolling sea, will not be sitting, will be standing leaning against the talll seat and holding on. I had no trouble with my seats and I installed them like I did because I did not remove the floor and had a good floor to anchor them into.

[Wildman]

Router out a couple ply's off the underside of your new deck pannel, Glass in a large piece of aluminum, (larger than the base of your seat) then drill down and tap the plate from above. You will still need to seal the holes from the top to prevent water from running in. It takes some planning, but IMOP its the strongest way of doing it.

[bigeasy1]

I like Wildmans idea about the large piece of aluminum in the deck and glassed over.I gave a lot of thought to a similar mount,but it was going to be a round aluminum plate bigger than the pedestal base placed on top of the deck floor with several countersunk screw holes in it.
I figured it would have given it a much more secure base and far far less chance of pulling out(been there done that).The glassed in plate mentioned, would be even better

On my Tsunami,I really wanted to be able to store equipment and other stuff under the seats,so I decided to somehow not use pedestals.We had a 150qt fish cooler that we wanted to slide under the stbd. seat,and other stuff under the port seat.
My buddy came up with this design,and it works good.Even with the weights of our fat butts, 250lbs ea. they are as solid as a rock.
I don't like the seats though and plan on replacing them at some point.

With the mounting points being in so many places there is no chance of the seat pulling out.
The upper mounting points on the liner are 1/4 -20 machine screws threaded into stainless inserts that we installed in the liner.(similar to a threaded pop rivet insert,only an industrial product)
The seats height is a wee bit to high,but not a big deal.The foot rests are at a good height for our feet,and if we're sitting sideways we can place our feet on the cross bars on the seat frame.

Here's a few pics.Not sure if it's visible,but the big cooler is under the seat,and at the end of the day we can place a lot of equipment under them and drop the rear curtain(last pic.)and out of sight of some of the prying eyes of the marina rats that like to steal easy to reach equipment.