Waterproofing non-treated lumber?

I have read it is unwise to use treated lumber in an aluminum boat because of corrosion issues. I added a front deck to my Lowe 1648 this week and I used regular SPF 2X4, mostly because most of the wood I used was scrap from another project. The only real new expense was the plywood and a box of deck screws. Eventually I'm going to cut out a door in the deck for storage/cleanout/trolling motor battery, but I want to figure out exactly where my seat should be. That's why it's on a moveable base right now.

My weatherproofing plan for the moment is just to slather it all with Thompson's Water Seal and then recoat periodically. Any better options? I have a big jug of boiled linseed oil if that would be better. My inclination is to go with something that is absorbed rather than a surface sealer like varnish or shellac. What's the general consensus on preserving wood in a boat?

I would focus on soaking the end grain with whatever stuff you choose.

I personally don't like the new formula Thompsons as it doesn't soak in like the old stuff did.

For the long haul, keeping it dry will make it last. Keep the bow up during storage & use a tarp if possible.

I'm not sure you need to waterproof it. It will spend most of it's life out of the water and the little bit of water that gets on it will dry quickly. But, if I was going to waterproof it, I wouldn't use Thompson's. Thompson's has parafin wax to make water bead up. That was also makes it penetrate poorly. Smart marketing because it makes it look like it's working when the water beads up in the rain. Around here, we have a product called CWF Flood stain that penetrates very well. It will last longer than Thompson's.

Old timers formula is popular with members on this site. It consists of mineral spirits, linseed oil and spar varnish. I'd have to search the ratio because it's been a while since I've used it. It soaks in well and also leaves a finish.

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I used old timers with 2 or 3 coats then let dry a few days then did 2 coats of spar. After a few years of hard use duck hunting my $100 build is holding up great.


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There’s a company called Totalboat that makes a penetrating epoxy for sealing wood. It works tremendously well, I used three coats of the stuff on my marine plywood transom. I thinned the first coat with Acetone, and the plywood ate it up. It’s very viscous, when thinned you can get it close to the consistency of water. It also takes a long time to kick off and dry, letting the wood soak up as much as possible. When I build my front deck I’ll be using it as a sealant and topcoat. I highly recommend the stuff!

CRS’s advice is probably the best idea, preventative maintenance is key. Keeping everything as dry as possible and covering the boat when done fishing will help the most in its lonegtivity. That and a good sealer and you’ll be in business.

Old timers absolutely. One part spar varnish, one part boiled linseed oil, 2 parts mineral spirits. Soak all sides of the wood until it doesn't absorb any more then mop up the rest. Let dry for 2 or 3 days. If it's going to be exposed to the elements coat with pure spar varnish. I did 5 coats on my decks then carpeted.