Seats mounted to floor

I'm installing an new aluminum floor on my Jon boat and was wanting to install some seats with removable pedestals on it. The floor is 1/8 inch thick and I know I need some back bracing under it to support the seat and swivel with all the forces on it. My question is what do you guys do for the backing and how do you mount it and attach everything together?


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Do you have enough space under that decking to mount the seat base w/o it hitting the bottom of the boat?

I have to go home and measure but I believe it will be ok


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You can always buy square aluminum tubing and make a frame that will act like a spacer to stand the seat base a bit higher up off the floor if need be.

Yeah my extra base plate is 2 inches or so to long do any seat bases that are removable not have that extra 3 inches below it


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Never mind on that last part


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lgpjr49 said:

Yeah my extra base plate is 2 inches or so to long do any seat bases that are removable not have that extra 3 inches below it
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Still no need to give up. Build up the floor as suggested above. Many ways to do it.

So if I build up with the tubing to get the height, do I still need some sort of backing under the main floor to keep everything from ripping out and the holes from deforming?


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Are the seat bases round or square? Not that it really matters.

You could get some flat stock or another sheet of 12"X12"X.25" and rivet it under wherever you are going to place the mounts which by doing that you could drill and tap the holes for the bases.

They would be square trying to make all my seat post interchangeable with all bases where they'll fit everywhere to keep down the amount of stuff in the boat if that makes sense


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I understand completely what you intend. I have 4 bases in my 16' and usually only have 2 seats in the boat. I just ask because it would be easier to build up the square bases as apposed to the round ones I have in my boats.

Check with your local hardware or home improvement store as most will stock aluminum square tube of different sizes. You can use that and miter cut the ends to match the size of the base then drill the tube to match the mounting holes. Then place a pc. of 1/4" plate under the deck and rivet it to the deck, then you will be able to drill and tap the plate to match the plate with the spacer.

At least this is how I would approach this.

Yeah I wanna put 2 more bases in the floor so I can hunt out of my boat if need be/ or a few more seats for bream fishing. So I understand the 1/4" under the floor then the tubing for build up so I can get my clearance, my question is how do you attach everything together? Just bolt it all before you attach the floor or is there something I don't know about to attach everything together?


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Cut a plate out of 1/4 inch aluminum a little bigger than seat mounting plate and drill the holes to align with the holes in the mounting plate. Put the plate under the floor the seat mount on top of the floor, drill holes in the floor and bolt together. Drill holes in your new flooring to align with your boat ribs and pop rivet in place. I use stainless screws and nyloc nuts. If you ever need to remove the floor, just drill the rivets out. Place the seat bases so they'll be between the ribs in your boat.

I've done three boats like this and never had a problem.

lucescoflathead said:

Cut a plate out of 1/4 inch aluminum a little bigger than seat mounting plate and drill the holes to align with the holes in the mounting plate. Put the plate under the floor the seat mount on top of the floor, drill holes in the floor and bolt together. Drill holes in your new flooring to align with your boat ribs and pop rivet in place. I use stainless screws and nyloc nuts. If you ever need to remove the floor, just drill the rivets out. Place the seat bases so they'll be between the ribs in your boat.

I've done three boats like this and never had a problem.

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This is pretty much what I did to mount the captains seat to the floor of my boat. It is a bell type adjustable pedestal though, not a pin mount type. Works great.

lgpjr49 said:

Yeah I wanna put 2 more bases in the floor so I can hunt out of my boat if need be/ or a few more seats for bream fishing. So I understand the 1/4" under the floor then the tubing for build up so I can get my clearance, my question is how do you attach everything together? Just bolt it all before you attach the floor or is there something I don't know about to attach everything together?


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Drilling and tapping the 1/4" plate would put threads in the 1/4" material for you to screw into - that's the "tapping part" that everyone is mentioning. Either that or J-nuts or U-nuts (more or less the same, sometimes called fender nuts, easy to find @ any hardware store). Pros & con's to each - the drill & tap allows you to use a stainless screw and thread it right into the aluminum plate - which is all nice and pretty well corrosion free (so long as you're not on salt water) but you're relying on threaded aluminum which fails if you over-tighten the fasteners. J-nuts you can tighten the hell out of, but I've not been able to find them made from stainless, so eventually they'll need to be replaced. I still used stainless screws with my J-nuts in my build...that way at some point the only thing I have to do is replace $2 worth of nuts every however many years.

lgpjr49 said:

Yeah I wanna put 2 more bases in the floor so I can hunt out of my boat if need be/ or a few more seats for bream fishing. So I understand the 1/4" under the floor then the tubing for build up so I can get my clearance, my question is how do you attach everything together? Just bolt it all before you attach the floor or is there something I don't know about to attach everything together?

Click to expand...

2 basic reasons for the plate under the decking.
1; provides a means of attaching the base to the deck. As is pointed out aluminum is a soft material so you do not want to over tighten and also use the largest diameter fasteners you can to attach the base to the plate. I use 3/8" fasteners. Also the thicker the material for the base the less chance there is to strip it or have it pull out.
2; most square seat bases are 7X7" So this dimension doesn't spread the load out very well especially onto a thin material like sheet aluminum or thin plywood that will give way or have a flex to it. This could cause the decking to buckle or pull the fasteners thru. So the purpose of the plate is to reinforce the decking and spread the load over a greater area. The greater the area the less it will deflect.

This plate should be fastened securely around the perimeter and also around the hole. Be it with screws and nuts or rivets. The tube that is used as a spacer can have the holes drilled so that the mounting hardware can pass easily thru it.

So then you can fit and mount the plate to the deck and then drill and tap for the mounting hardware or you could just drill and bolt the bases to the decking before you install the decking. Either way works.

The whole thing to remember is that you want the bases to be sturdy and ridged so that when you are sitting in the seat the base, post, seat and deck are not going to move when you change position in the seat or getting bounced around by waves.