Marine Plywood

Discussion in 'Boat Modification Journal' started by Chalk, Jun 17, 2009.

  1. Chalk

    Chalk New Member

    Messages:
    126
    State:
    Union, South Carolina
    Does anyone know where to purchase Marine Plywood near upstate SC? I'm redecking my Pontoon and need 4 sheets.
     
  2. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    Tell me why you want marine plywood for a pontoon deck first.
     

  3. Chalk

    Chalk New Member

    Messages:
    126
    State:
    Union, South Carolina
    most everything I have read says to use marine plywood instead of treated. Give me your take on it. I would much rather use treated for the price alone but I do not want to be redecking this in a year or two.
     
  4. Iowa_Josh

    Iowa_Josh New Member

    Messages:
    1,463
    State:
    Central Iowa
    Kevin, Mark's on rampage about the plywood today. You can look in the boat mod section and read it. If you go way back and read in the archive, there's some good info (at least I thought so) from some more experienced economy boat builders. One I remember was regular plywood painted a bunch, like four heavy coats and sand sprinkled in the top coat. I'm making the four coats part up, but I'm sure it was more than one and the edges were well sealed. I don't know if they stated what kind of paint.
     
  5. Iowa_Josh

    Iowa_Josh New Member

    Messages:
    1,463
    State:
    Central Iowa
    That treated stuff is extra heavy, can't be painted until it dries out and you have to use specially coated screws with it because it corrodes. Is your pontoon specially treated so it won't corrode?
     
  6. Flamekeeper

    Flamekeeper New Member

    Messages:
    2,314
    State:
    Louisville, Ken
    For 6yrs I welded and built Alum Yachts and houseboats and yes you can use the marine/treated ply. We did on 125' boats..Just make sure you paint or coat the surface its coming in contact with something a couple of times before securing it down, using 1 1/4" Deck screws in pre-drilled pilot holes.

    Get some 7/8 tounge&groove it will be there for a lifetime..You can spray the bottom side with a marine grade hull blackcoat/sealer if needed..
     
  7. lendog

    lendog New Member

    Messages:
    2,141
    State:
    berks, PA
    i used 3/4 inch marine board on a jon boat and it was very heavy, made the boat very stable and i'm sure it will last forever but wish i used 1/2 inch insted.
     
  8. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    Treated plywood will outlast marine plywood if all you are doing is screwing down plywood.
    Marine plywood is NOT treated in any way shape or form to prevent rot.
    What makes marine plywood is a totally different set of parameters having nothing to do with rot. It's strength and weight primarily. In fact species of marine plywood like Okoume (Gaboon) is light in weight compared to most others but is not very rot resistant compared to say pine or fir.

    Marine plywood is a good choice. The best choice for it's strength in both shear and the lateral plain however it has to be coated with epoxy and I would recomend on the deck side laying 6 ounce glass cloth for ding and dent protection.
    A sheet of 3/4" treated weighs around 86 pounds. A sheet of Meranti will weigh around 50. Spread that difference over 4 sheets of plywood and you have saved quite a bit of weight.

    Marine plywood has near to perfect laminations. No voids like you get with domestic plywood. It also has more laminations making it that much more stronger.
    A 3 gallon epoxy kit should be plenty for that floor. 155 bucks plus shipping.

    Properly installed it would be a floor that would outlast the pontoons.
     
  9. Spider

    Spider New Member

    Messages:
    610
    State:
    Hamburg, PA
    I bought one shhet of Marine 5/8 to make a new transom insert but the rest of boat I used exterior plywood. The 5/8 marine sheet set me back like $78! Too exspensive for my budget.
     
  10. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    Alot of people equate the sole in a boat to the 3/4" underlayment in a house for some reason.
    2 Different type loads and demands.


    78 dollars a sheet for 1/2 is a little steep unless you were buying Okoume.
    But for Meranti that is steep.