is the center bench seat in a 14-16 ft necessary for structual integrity of the craft?

this is done to make a flat floor thus enabling easier movements from back to front.

some say it greatly weakens the boat, others say not so.

what is the downside if any to doing this modification?

Yes it will.A friend of mine made me a ribed piece of stainless steel that we rivited in and it worked fine.

The seat is most definately an intergral part of the structure of the boat. By removing it, it will weaking the hull. You need to replace it with a true rib.

What everyone else has said. If you go to tinboats.net you will see several examples of boats that had the seat removed and examples of how they reinforced the hull

I reinstalled my center seat after I noticed the hull flexing and stress cracks starting to appear at transom braces.

Wow, thanks for the great advice folks.

hello again, considering removal of middle seat from a 1448 alumacraft jon. this boat has 21" sides, center seat with dry storage and hatch cover, and many ribs from 2/3 the way up the sides and across the bottom inside the boat.

i checked the tinboats website and found others with the same boat have removed the center seat. could it be that this version of alumacraft jon boats have a hull strong enough without the center seat?

We build aluminum Duroboats.

Your question regarding moving the middle seat is a common one and unless you are dilligent and a good fabricator it may not be a good thing to do.

As a builder and I think most builders would agree.

THE BIGGEST REASON NOT TO REMOVE THE CENTER SEAT IS

Most aluminum boats use that center seat to house flotation that is critical to yours and your passengers safety in the event the boat is swmped.

Boats smaller than 20 feet require flotation enough to ( when swamped) hold up the rated capacities, ideally in a level flotation attitude.

If you are determined to make the modification. Consider: If you make the change most builders would nullify any remaining warranty.( possibly not an Issue for your boat if it is older).

When you take the flotation from that seat you should find space high above the floors and where possible near the perimeter to re-install compensating flotation sufficient to float the rated capacities.
It must be retained in such a way as to protect its structure and keep it in place under all conditions.

On many boats you will weaken them by removing the middle seat. I Doubt you are working on one of our boats as we don't sell many in Texas. Tomorrow I will drive to Texas in hopes of changinfg that but tonight it is not likely. .

To further discuss your goals I will use our boat which is very tough as an example. On ours you would certainly not make it stronger with your change but it would likely hold up better than most. The biggest risk is repeated flexing from use in big rough water or trailering on rough roads. The middle seat reduces flexing at thew midpoint of the boat. It logically without a major element of support would not be as strong as it would be with it. The marginally less strength could allow the sides to flex more than they might otherwise and over time could induce breakage. Proper restructuring and replacement bracing as discussed by others could prevent that. In our walk through model boats, designed to provide exactly the room you seek, we relocate flotation and use side boxes for bracing. We add significant structure to the boat in other ways. Some structure is below raised and widened decks and out of the way of photos but you may look at pictures of our boats and other brands to try to decide how more open boats are done and yours can be done safely. Typically the open boats with proper structure are more costly than the simplified 3 bench models. If you do the work yourself it is best not to skimp on material or structure. Keep the added weight you add in mind as you compute flotation needs. Coast Guard publications are available to help small boat builders that can be good referrence for small boat modifiers.

Whatever you do, stay safe and be conservative in making sure your boat is just as safe after your mod.s as before.

Good Luck.

PS if you summer in Wisconsin check out the Waupaca Chain O Lakes, mid state. If you are or want to be a Waupaca fan find and read NORTH TO WAUPACA on Line.