Marine grade plywood?

This last week I pulled the trigger and bought my first boat. I got a great deal and part of the issue is that part of the deck needs to be replaced. I understand that I need to use marine grade wood but Im not sure I understand what that is or where to get it.

I tried to google something in the Austin area but am coming up with nothing. Where should I be looking? Boat specific places, home depot? Anyone know a place?

No need to use marine grade plywood. It is absolutely ideal, don't get me wrong, but it's not required. A good ABX or ACX (but nothing lower!) exterior grade plywood will work just fine. It will save you A LOT of money!

In terms of where to get each:
Marine grade - check with a boat yard or marine shop. SOMETIMES you can find it in a lumber yard, but not too likely. A Google search should have yielded plenty of suppliers. Be prepared to pay out the arse for it.

ABX/ACX Exterior - Most decent lumber yards carry it at a reasonable cost. Usually easy to find locally.

Regardless of which you ultimately decide to go with, be sure you coat it 100% with resin and a layer or two of (at least) 3/4oz CSM to make it waterproof. Even marine grade plywood is NOT waterproof.

Also, don't do just part of the deck. Do it all! If part of it is rotted, then it's only a matter of time before it is all rotted. Moisture and rot is already in it and it will continue to spread, even if you just replace what is bad now.

Thanks for the reply, great info. I guess I didn't word my first post right, I found suppliers, but I was lookin for a place to drop in and pick a couple of sheets up from and couldn't find that.

As for the deck, The front and rear of the boat are elevated and that wood is in great shape, the whole bottom portion is what was bad and was removed. I was thinking this was going to be a simple cut and screw down operation, looks like ill have to do some more homework to make sure I end up with something that will last. I appreciate your input!

Just drop in to a lumber yard/Home Depot/Lowes and go with ABX or ACX exterior plywood. Stop bothering with trying to find marine grade.

If your two upper decks are fine, then they're fine. The only wood that you're going to have to replace is any wood that is in direct contact with the wood that is bad.

That said, and even though I recommended to replace it all, you could possibly get by with only replacing part of it. For example, if your bad spot is in the front left section of the deck, then you might be lucky and have perfectly good wood in the rear right section of the deck. It all depends on how far moisture and/or rot has penetrated. You COULD just cut and screw in new wood, but it's not going to last long.

The first thing you need to do is fully assess the situation. Only then will you know for sure just what needs to be done. Yes, I recommend doing the entire deck as that will provide the best assurance of a long-lasting fix, but you need to be the judge of it. If you only end up replacing part/half of the deck, it may last many years or it may end up only buying you a few years.

Another thing that you will need to check is the stringers. If the deck rotted out and it was screwed directly into the stringers without being sealed, then rot could have infiltrated them. When you cut away the deck, make sure the stringers are good! What year boat is this, by the way?

Regardless if you replace the whole deck or just cut away the bad section, be sure to coat ALL exposed wood with fiberglass resin and a layer or two of CSM. You don't want any exposed wood for water to be able to get back in to, causing you to have to repeat the process again down the road. Fix it once, and fix it right.

only thing I would do different than nax's method is use e-glass (cloth) instead of roving. much lighter and for a deck just as durable. roving soaks up a lot of resin, cloth not as much.
you can buy either at wally world in the auto repair area, comes about 4 sf per package.

Texas-z, congrats on your first boat. If you feel like you need some help feel free to stop by our shop and we can give you some help. Gary Pender 512 250 9000.

Here is the boat, paid $700 for it. Its a 1987 Traveler, 16ft alum flatbottom with a 40hp nissan outboard.



I bought it from a gentleman that I work with and when he was getting it ready to sell the motor was running a little rough, he refused to sell it to me in that condition so he went and had the motor tuned up and now it runs like a dream.

There are some issues, gas tank needs replaced, dents and dings, the deck needs put back in and the steering cable needs to be routed right.

He removed the deck himself, so he is what it looks like at the moment.

might get some ideals from this post..

http://texasfishingforum.com/forums/ubbthreads.php/topics/7121060/Monstaliner_boat_floor#Post7121060

If I was plannin on keepin it for a pretty good while Id check on a piece of alum.sheet (doesnt look like that big of area)the floor in my deckboat is alum. no ply at all

Ah, a 'tinny'! Makes it much easier for ya! Stick wit h the exterior ply I mentioned and coat it with resin and roven (I agree with hop on it vs csm). With the deck already pulled, just cut/fit a few sheets of wood (cut/fit BEFORE you 'glass). Lay it down and drill your pilot holes. Fill with an rtv or marine sealant and screw it down with stainless steel screws. Then you can carpet/gelcoat/paint/bedline to your liking. You'll be good to go for many years!!

Only other suggestion I have would be to replace/add foam while you have access. That old stuff is an open cell foam and soaks up the water (which adds weight and decreases emergency floatation). A good closed cell is a much better alternative. You can get the pink sheet foam at Home Depot fairly cheap or you can buy a 2-part expanding foam. Simply cut the sheets to fit before putting the deck down. If you use 2-part, drill holes in the deck above every 'compartment' and mix/fill until it expands out the hole. Shave it down and youre good to go.

Sorry for the rambling and lack of structure. I'm posting from my phone.

get the pink or blue rigid foam board in 3/4" at lowes, cut to fit leaving airspace between it and the deck bottom. I would not use the expanding in that style of hull as it will prevent water from running back to the bilge area. I would also pull the side panels (the ones with the holes in the pics) and put foam in them till they are full. place a good bilge pump in the very back and leave a hole for access/visual (about a 6x6" is good).
paint the floor with a good oil based enamel or epoxy paint (I prefer the epoxy) and sprinkle a little sand on it while tacky for traction. paint over again when dry and you will have a great floor for that style boat. if your going to mount a seat behind the cc be sure to have at least 3/4" ply for the base to screw to thicker is better. I would also go to fastenal and try to get some aluminum screws to avoid the electrolysis that will happen with 2 dissimilar metals like aluminum and stainless, stainless is good if you can't get the aluminum.
done right that boat should last a good long while and with what you paid you got a great deal.

I agree with all the comments on Marine grade plywood. The only reason that you would use marine grade is because there is no voids or "football" plugs in the laminations of the wood. Therefore it would be suited for impact resistance if you were building a hull. I mix 1 part resin and 3 parts acetone and add hardner for 4 parts and roll this mixture on both sides of the plywood and especially the edges. I do this three times. The plywood will absorb the resin and make it waterproof. Do this after you have your pieces cut to fit. You will be happy with the longitivity of your labor.

Mike, I think it's important to note that if you're just going to use resin (no fiberglass) as the waterproofing agent, then it really needs to be epoxy resin. Polyester resin by itself is brittle (especially if mixed too hot), thus making the waterproofing deteriorate over time as the stress and flexing slowly cracks the resin.

If I was going to coat the deck without using fiberglass, I would use polyester first, as it soaks into the wood better, and finish it up with epoxy resin to have a tough outer coat that will be less likely to crack over time. I'm still a fan of using resin with glass, though.

Good points from hop, as usual! You can still use the 2-part expanding foam if you want, but you need to be very mindful of the water channels. It's easier to use 2-part in a 'glass boat with middle stringers. In yours it looks like the sheet foam is going to be ideal (and it will be cheaper!).

You miss the point. 1 part resin w/ 3 parts acetone. I am using the acetone to thin the resin so that it is absorbed into the fibers of the wood. I am not coating the wood with resin but allowing the wood to absorb resin which makes it waterproof. Once the wood is waterproofed then whatever top coat you want to apply wheather it is fiberglass mat/cloth or paint is entirely up to you.
This is an old boat building trick that has been around for decades.

No, I got ya Mike. I wasn't aware that adding acetone would help it penetrate/absorb better. I'm by no means a pro at it. I'm just a backyard boat restorer and I tend to "overbuild" as a result.

I don't want to derail this too much, but I'm curious about this method. I may give it a try myself. It doesn't seem like it would be any cheaper, but it sure would be a lot simpler/quicker! Does the resin/acetone mix saturate the plywood entirely? Once done, is there any sort of encapsulating barrier around the wood or does it end up just being resin impregnated wood (i.e. able to be sanded without losing the waterproof abilities)? What happens if/when the wood cracks (if even possible); will the newly exposed wood inside the crack still have waterproof potential?

I usually apply three coats on each side. Each coat takes longer to cure. I've not had AB ext plywood separate after doing this treatment, or at least not while I owned the boat, up to four years, weather exposed. I just did a pontoon deck this way, three coats on the bottom side, then a coat of exterior latex paint, Top side, two coats, then fastened the plywood down to the cross members, followed by one more coat and paying peticular attention to the edges. Then covered with marine grade carpet. Only time will tell.
Since the AB ext is five ply, I know for sure that four plys are saturated. Have not checked the inner most ply, since I prefit all my pieces prior to the saturation process, I have not cut into the plywood to find out. I really pay attention to edges and IF holes are cut in the plywood, I make sure they get a liberal dose on it's edges too.
Now if I apply resin soaked fiberglass, I try my best to get a 65/35% ratio. 65% glass, 35% resin. I have done vaccuum bagging, in the past. That process is the most perfect way to achieve the proper ratio. But when laying glass, I use a squeege, or bondo spreaders to get as much resin out as possible. Cause everyone knows resin gets brittle and will crack if left to dry too thick.

Cool, thanks for sharing Mike! Sorry for the misunderstanding.

Texas-Z - In case you didn't catch any of that, either method is going to work for you. Mike's method is going to end up being easier, I'm pretty sure.

Texas-Z , Thanks for the call yesterday and feel free to get back with me if you need anything more.