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Marine Plywood Question

Discussion in 'Boats and Motors' started by crankus_maximus, Mar 8, 2005.

  1. crankus_maximus

    crankus_maximus Crankus Baitus Maximus

    I need to replace some pieces in my boat and I was wondering if there are different thicknesses of marine plywood available. The pieces I have to replace are the tops of bench seats in my boat that are currently split and coming apart. They are covered in indoor/outdoor carpet currently and I don't have to cover them back up, although it wouild look better. Is there another material I could use in place of wood that is light-weight and durable? Can I use treated plywood in place of marine plywood? Decisions, decisions! :eek:
  2. misfit

    misfit MOD SQUAD

    go with's lots cheaper,and will last for can get it in 1/2 or 3/4 inch.seal it with a good sealer,and you'll have no problem.a lot of boat manuf's use it in place of marine grade,and gaurantee it for 10 years or more.

  3. The price of Marine plywood is like "wow" buying gasoline. I found a repair shop that cut me a small piece that I used to replace a transom.

    If you have an aluminum boat be careful, it does not like treated lumber..

  4. crank- I agree with Misfit- treated wood works great- sand it rough and throw minwax "spar" urethane on it couple times- will last longer than you!!!

    Many guys including myself have rigged our little alums for lado with this- my deck 8 years later is like a rock- I replaced the transom two years ago too and very very solid- these little rigs stay drenched - kept mine outside storage for 3 years- still perrrfect.

  5. misfit

    misfit MOD SQUAD

    i haven't done a lot of research on that subject,but from my experience,haven't seen any problems.i'd think if it was that much of a problem,they wouldn't use it in "new" aluminum boats,and i replaced the transom on my aluminum boat last year with it.the old transom was treated,and it was 25 years old,and i saw no damage to the hull.
  6. A boat repair shop showed me small dotted holes in the bottom of an aluminum boat hull that he believed came from using treated lumber in the trailer supports that were covered with I/O carpet. This was in a salt water condition.

  7. misfit

    misfit MOD SQUAD

    i'm not sure,but i'd think the saltwater might be more of the problem than the wood.
  8. When I was in S.C. we used a small aluminum boat to fish for huge crappie and the guy that let us use it told us to rinse that brackish water off by turing the boat upside down on some horses he had for that purpose... Then showed us the bottom of another boat that was never rinsed and it was pitted pretty bad...
    I am guessing Rick hit it on the head
    BTW... if you seal that wood so it does not leak then problem solved... Treated wood does leak somewhat...
  9. Those pin holes are often the result of grounding electronics directly to the boat itself. Treated lumber won't cause that. Also, make sure to use stainless hardware. Regular hardware will react with the aluminum over time.
  10. sowbelly101

    sowbelly101 Keep'n It Reel

    only problem i can see with treated lumber is it has a tendancy to warp when it ages. i was looking for a piece to use for an additional deck storage compartment that i cut into the front of my boat and when i was checking out the treated it was pretty wavey already. since it was only a 14"x15" piece i used regular plywood and put a few coats of poly on it. not sure how long its going to last but it was cheaper and wont be to hard to replace if it wears out every year.

  11. crankus_maximus

    crankus_maximus Crankus Baitus Maximus

    These are just the tops of the bench seats ina 14ft semi-v. I'd like to do more, but I have a 17.5 ft lund or Alumacraft in my dreams for the next year or so. This one is just going to get me through for now. The wood does have to be strong enough for pedastal seats (already in there now).

    Do you guys glue the I/O carpet in? Or, should I just paint it with some oil-based grey paint to match the boat? What do ya think guys?
  12. misfit

    misfit MOD SQUAD

    3/4" ply should work for the seats.use a good waterproof glue for the carpet.if you don't want to carpet,then paint 'em.guess it's really in what you personally would be happy with :)
  13. I agree with Rick, whatever you think will work for you. Marine carpet will always look the best, but if it's just temporary, paint would work fine. 3/4" will be plenty to hold the seat, as long as they're fastened well.
  14. I'm not positive but I think the treatment is for insect-protection. That's what I've been told on new home job sites.

  15. misfit

    misfit MOD SQUAD

    insect protection is one benefit.the chemicals also prevent fungus growth,which i think retards rotting. because of it's durability and long life,pt wood is used for everything from boat docks to home foundations.
  16. If you are going to do the work then use marine grade plywood. Although it is a bit pricier it will last much longer. I have used both and the pressure treated warps and it shrinks. I have used it on pontoon boats and had it to shrink as much as ¼”. This causes your seams to have a gap and lets them warp.
  17. A method that I have used in the past that is somewhat expensive, but quite durable: Use a marine grade plywood, coating both sides and all edges with a mixture of fiberglass resin and hardener. Make it up at the same ratio as if you were using fiberglass cloth, but skip the cloth. Allow the resin to cure before installing the pieces.

    You'll end up with a durable, waterproof finish. With this, the wood you install should be pretty much "lifetime". Most auto body supply shops will have the resin and hardener in stock.

  18. misfit

    misfit MOD SQUAD

    shrinkage and warpage will occur with any wood,when it's "green.letting the pt dry out for awhile,while weighted down before installing,will eliminate that problem.sealing and proper installation will help prevent further warping,and assure many,many years of service.
  19. I'm with Rick on this one...
    we have built small docks with treated lumber with great results thus putting it on a boat out of the water would not be a problem
  20. crankus_maximus

    crankus_maximus Crankus Baitus Maximus

    Cool. I'm going to try and post some before and after photos to let you guys know how it turned out. Thanks for the advice. It was greatly appreciated!