Aluminum Boat Floor Replacement

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  #1  
Old 07-19-06, 12:49 PM
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Aluminum Boat Floor Replacement

Anyone have any thoughts on this floor replacement project ?

Project: 1972 Starcraft Jetstream, 72 Merc 500 50hp

The motor has a weak but steady stream (seems weak compared to 86 johnson) after installing a new water pump and housing

Tried it out and it planes easily and runs about 25+ with 2 people in it.

Problem: Floor Rotted out (removed by previous owner) so I have no template to work with, seats and floatation billets are MIA as well. I have the aluminum strips that were under plywood and the side gunnels.

Problems: Floatation

I want this to be a fish/ski boat primarily for the kids and the cheap way out seems to use 2 sheets of 1/2" treated plywood. Stainless Steel screws... i/o carpet.

Alternatly steel rivits are cheap and easily had ?

Was amazed at how hard it was to find marine plywood and suitable fasteners (aluminum or ss rivets big enongh for 1/2")

I contemplated 3/4 treated because I had some on hand but did not want to contend with the extra weight, or the fact that the sides gunnels would not fit over it.

I am hoping this will last 5 years, and I dont have alot of money.

The right way $$$... maybe marine plywood or plastic "STARBOARD" and Aluminum rivets with large flange.

Thanks In Advance
Mike
 
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  #2  
Old 07-20-06, 09:12 AM
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First off, stay away from the Starboard. Not what you want for the application. As for a template, use cardboardto get the right shape, then transfer it to your sheet goods. Try not to use rivits if possible, it really limits you if you have to take the deck up. What I did when I built a casting deck for a guy, was where I had to attach to the aluminum, I drilled and threaded or put in nutserts if I had the room. That way I could use machine screws, so the holes wouldn't elongate or strip taking the deck in and out. A good marina will have all the stainless hardware you need. Can you use 5/8" ply?
-Chris
 
  #3  
Old 07-20-06, 01:45 PM
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All the local lumberyards only stocked 3/4" treated, only lowes had 1/2" instock. Does the 5/8"'s have more ply's and or just fell less springy and last longer ?

I will go back and look for SS screws at the marina I know lowes stocks them, none of the local marina's big or small seemed to eager to help me find another supplier for marine plywood or rivets.

I could order rivets aluminium were .12 ea min qty of 500, ss I think were .65 ea 100 qty... SS screws are probably more expensive but I probably can get smaller qty's. Hopfully I will never have to take the deck up, but the next guy will appreciate it.

Did you use washers or a large heded screw ?

Did you put carpet on before you screwed it down or use glue?
 
  #4  
Old 07-20-06, 09:46 PM
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As far as a supplier, call a local boat yard who actually does large repairs, they should be able to hook you up. I have a couple of yards here that are great. 5/8" has more plys than 1/2, but less than 3/4. so it's pretty stable stuff. I acutally used a good AC grade, then sealed it with resin. You could probably get away with sealing it with polyurethane. I put the carpet on first, then used fender washers with #10 pan head screws. The reason I went with fender washers was because the increased size gives less chance of pulling the carpet edge down through the hole and making the carpet hole bigger.
-Chris
 
  #5  
Old 07-21-06, 07:01 AM
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I went to the biggest marina in my neck of the woods last night and they did indeed have a large number of SS screws and other hardware.

They reccomended #14 1" or 3/4" flat head screws for 1/2" ply these have pretty good size head.

They really want a huge markup on any plywood, and basically told me lowes was the place they would get any treated.

You paint reg plywood or treated with resin ?

When I was down there I pulled back the carpet on a brand new smokercraft boat, an was interested to find they dont use very big rivets. They use a slipproof rubberized matt lightly glued down to 3/4" ply (i think) and then put in regular snaps to hold down a top layer of carpet...

My other issue is floatation, they had a 2 part pour in foam available at the marina, that looked interesting I suppose that would keep moisture away from the underside of the deck ( or maybe just trap water ) I assumed that I would be able to find free floating foam billets like the origional ones that came with boat allow water to pass by and out the drain.
 
  #6  
Old 07-23-06, 09:28 PM
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Wink

I have used the mix foam and it can grow on you and lift the floor . Id get some blocks of polystyrene. Cut and fit them under the floor. This will let water drain out. later on if the boat gets to heavy you can pull them out and put new ones in. With the floor screw down.

ED
 
  #7  
Old 07-26-06, 06:26 AM
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The two-part foam is for putting inside voids or inbetween fiberglass, like between a transom and the keel. I would go with Ed's recommendation and use poly styrene. Did the original configuration have flotation under the deck? I'm not familar with your boat, is the hull fiberglass or aluminum. The foarm that will last a lifetime is the high density block, used under floating piers. Cuts with a bandsaw really nice (but messy). After that, you can use the pink foam insulation you get at the Depot or Lowes. Depending on how much room you have under your deck, you might consider attaching it to the underside or your new deck. That way you wouldn't have to glue it to the hull (I don't know how else to attach the stuff), and when you pick up the deck to clean out the bilge, it
s out of the way.
-Chris
 
  #8  
Old 07-26-06, 06:16 PM
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Outstanding feedback so far. As an amateur boatbuilder and avid boater (means repairs a lot of watercraft) - I've always had a problem obtaining "marine plywood" - to the point that I gave up on trying. I use A/C exterior grade and have had outstanding results - especially when I seal it with fiberglass resin. Last boat I built out of it (21ft Jet Boat) - lasted 10 years without sign of wood rot or deterioration.
 
  #9  
Old 07-28-06, 12:49 PM
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"Just what I have found out over the years." From the wood GUYS. if you check the ply# and its the same the only differents from the marine plywood" to the A/C exterior grade is that the exterior one has voids in the inside of it, with a lamp on one side of the ply you can find them sometimes and we fill them with some epoxy with a needle. They tell me its the same glue.

ED
 
  #10  
Old 08-01-06, 03:18 AM
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Marine ply will also have a paper coating on each side. There are two grades, MD and HD. The difference betweent he two is the amount of plys and the thickness of the paper. The HD is usually 5/8, and the only sealing you have to do is the edges. The MD my need a coat of resin over the paper depending on application. Either way, the expense usually isn't worth it when you can get 3 sheets of A/C grade for the price of 1 sheet of HD.
-Chris
 
  #11  
Old 08-01-06, 03:39 PM
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You could also check out Baltic Birch plywood.. The layers are thinner and there are no voids in it..
 
  #12  
Old 08-01-06, 11:38 PM
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Baltic birch is a very stable plywood. Great for cabinetry because of the high layer count, and the lack of voids like Axl said, but in an application such as this, the cost would be prohibitive. Plus it's a bit painfull to think of that nice cabinet grade ply under carpet, covering the bilge of a boat.
-Chris
 
  #13  
Old 08-02-06, 04:15 PM
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Red face floor

where i work a leading marine manufactering company we use a lot of marine plywood from 1/4in up to 1-1/2in marine plywood is void free you are better of with exterior plywood and resin helps if you spray it on (better coverage) as for the foam there is a company called redi-foam comes in a container like a 20lb propane. the foam
is to keep the boat from sinking when you take on water!!! dont skimp on it
 
  #14  
Old 05-31-09, 12:09 PM
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Plywood update

I used 1/2" treated plywood and stainless #14 x 1 screws and after 2 seasons of use it's held up well. We pulled it up and checked this week and put in a wood block under a part of the floor that gets a lot of use that's right on a seam.

I had tried a few rivets in the installation as well and some of them had let go, screws worked a lot better.

Treated wood did not seem to cause any problems of corrosion, and showed no signs of rot.

The boat sees a bit of action, every nice weekend and is stored outside in the Michigan winter with a tarp overit.

Overall it was very economical fix, next we going to get bench seats, we just used cheap plastic ones and pedestals this time.
 
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