Aluminum boat - Saltwater corrosion repair

I have an older aluminum run about that spent most of it's live in saltwater. I am in the process of a complete redo and have to deal with some corrosion pitting and some perferation. It's not major, but theres a few spots where the wood floor braces sat on the aluminum that have some deeper pits and a few go through. I had it in the water, and the leaks were very minor. I would have never noticed the pitting if I wasn't under the boat in a dark garage trying to adjust the trailer to fit. I could see light through a few of the pitted areas. I cleaned and spot blasted the pits, and was wondering what the best and most permanent way to fix them would be. I ruled out welding since that would cause both warpage and posibly create more problems if there's any other spots that are close to going through.
What I was thinking was to fill the pits with Marine Tex aluminum epoxy, sand them smooth and then Gluvit the entire inside the the hull. It's getting a fresh outer coat of epoxy paint when it's all done too, so that will also help seal things a bit. The rivets are all good, none loose and none that are deteriorated from corrosion. There's alot of lighter pitting over the whole keel area but nothing that gives me any real reason for concern. It was being used when I found it, and it was regularly left in the water and never sank and never had a bilge pump. I think the worst thing they did was to bottom paint it with copper based bottom paint, I think that created most of the corrosion pits from electrolosys effect due to the paint, copper and aluminum. It had no electrical system, only a magneto start outboard so the lack of a battery and any stray volts may have saved it some too.

My question is, will Gluvit work on bare aluminum? I am familiar with the self etching primer that's used on aluminum, but I am not sure whether or not I want or need primer under the epoxy and sealers?

I also plan to reinforce the transom to allow a slightly larger motor, the original design is only a single wall with very little diagonal bracing, I plan to add a double wall and motor tray and run a larger motor. The way it is now, it can't be rated for much more than an 8 HP. The boat is 16' long with a 66" beam. I can't imagine what they were thinking with that style transom. I've seen 10' jon boats with more transom support.
The hull design is what got my interest in this, it's sort of a cross between a V hull, a flat bottom and it has some hull lines of a trihull in the front and it's made of a single piece of aluminum, no seams or welds. I've never seen another hull like this, its made by Duracraft but I have no idea what year. The title says 1971, but it was renumbered then by the marine police as an abandoned boat. It was in use since then by the former owner as a personal fishing and crabbing boat. He was running it in the ocean daily.

Here's a pic of it when i first got it home:
Any ideas as to it's true age? There's no numbers to be found other than an added on plate from 1971, so it's at least that old. It's got a semi closed bow, and no windshield, the front area is a storage compartment with two sliding doors. It's tiller steered with a cable system like an older sailboat. Everything is aluminum with only the exeption of the wood floor and steel tiller handle.

Re: Aluminum boat - Saltwater corrosion repair

let me know when you figure it out. after i finish the Duracraft. i'm going to have to tear apart my Bluefin, i redid last year. just found the same problem. thought it was loose rivets.

Re: Aluminum boat - Saltwater corrosion repair

Reelfishin, Epoxy putty like MarineTex will bond very well to the aluminum, provided the surface is clean, and there is enough thickness to the metal. The issue you will have is consistancy of thickness of the putty and possible cracking of the putty, due to flex of the hull during use. You might embed some fiberglass cloth into the putty to give it flexible strength. I repaired a steel gas tank this way, and it has held for years, thru flexing and expansion. Obviously, if you repair it on the inside, the outside of the hull will stay hydrodynamic. if you paint the inside, likely the repairs will be nearly invisible.

Re: Aluminum boat - Saltwater corrosion repair

I keep getting conflicting info from both the paint shop and the local marine supply that sells both the epoxy and and aluminum putty. They do repairs there, so I figure that they have to have some knowledge or the products and the paint shop is only reading the lable and going by what their other customers relay back to them. I've painted aluminum before, and even items I painted long before I ever heard of self etching primer have lasted just fine. But yet I've had a few aluminum items that shed the paint like a snake shedding it's skin.

Re: Aluminum boat - Saltwater corrosion repair

The perforated spots are so tiny you can't see them without it being dark and a bright light on the top side. I had it in the water and the leaks were so minor I wasn't sure if it was a leak or just wet hands the dripped in the boat. I intentionally floated it with the wood floor out for that reason. I wanted to see what was and wasn't going to be a problem. I was told by someone at West Marine and also an epoxy manufacturer that I should clean and prime the area to be filled first. That didn't make any sense since one of the first instructions on the package of Marine Tex or even the Devcon Aluminum putty I have here says to start with clean bare aluminum. I've use the stuff to repair broken skegs, chipped castings and other much higher stress items and it's proven pretty indesructable. I built up a chipped skeg on a 25 HP outboard in a hurry about 10 years ago, with the intention of cleaning it off later and rewelding it when ever I had to reseal it, but it's been fine ever since, with no signs of the patched area coming loose. There's about an inch of the fin that's made up with Devcon marine putty, sanded and repainted. It's only about an 1/8 thick and it seems as strong as the aluminum.
With that as a strength comparison, I would suppose that using it to fill the tiny pin holes would be fine. Besides, I plan to coat both sides when I'm done anyhow. The pin holes are so few and so small, I suppose just paint would probably fill them in and seal the hull, but I just want to make positively certain it's permanent before I redo the floor and the paint.
Someone told me that Gluvit requires a primer? I haven't seen a can of it here in hand to see for sure. I am going by what a salesman online told me on that, who may or may not be correct. The hull is either powder coated or primed with something already, the outer paint is pretty tough to remove and I don't intend to remove it anywhere it's stille adhered well. I don't see the need to disturb a bond that's already in good shape. I used a fiber abrasive wheel on an angle grinder to remove some of the bottom paint, it takes off the antifouling paint but won't touch the original paint, so what ever they used it's well adhered. The only place it's off it around the front and on the transom where someone has actually ground or sanded it to bare aluminum. The front looks like it's just worn off over the years. The only corrosion or pitting is under the antifouling paint where it was applied over bare aluminum spots. The inside of the hull looks like new from the top with only a few areas that have some flaking of the paint on the bottom.

I've also been thinking about whether or not to retain the old style tiller steering or go to a modern single cable system? Whats there works, but takes up a lot of space, with the pulleys and double cable run. I've never run a boat with this type of steering, I've had tiller steer boats but never one this old. I like the idea of having a clear floor with no console in the way, it leaves the boat wide open. It also had an old twin stick OMC control unit, which I hope to keep even though I will run a much newer motor.

Re: Aluminum boat - Saltwater corrosion repair

have you every thought about using the ez gulde stick steering. i had it on 2 boats, and like it a lot.

Re: Aluminum boat - Saltwater corrosion repair

EZ glide is an option, I prefer to stay with a tiller handle, it saves so much space and allows me to sit up front and drive, since I am usually the biggest person in the boat, my weight helps the boat handle and get on plane up front. The only drawback is that I have to rely on someone at the rear to tilt the motor when needed.
I am still working on getting all the hardware off the hull, most of it is too far gone, but I've been trying not to tear up the aluminum removing it. I have new stainless steel pieces for most parts, but for the cleats, I'll have to find the older three bolt rocket shaped style cleats like they used on some older mahogany boats. The modern cleats won't cover the holes and I don't want ot have to weld in or fill unused holes on top. The rub rail will have to come off since the ribs and livewell are riveted through beneath it. I'll have to try to match up new rubber insert for it too. It looks pretty common so that shouldn't be too bad, the old one may even survive removal.
The center keel on this is super heavy duty, this looks like they intended it to break ice or something. It looks like it's about an inch thick at the front, and it flares out about 4 1/2" wide. I like they way the minumized the use of rivets, the keel is riveted, the center rib has to rows or rivets, and the transom is outlined and secured with rivets, the rest of the ribs are welded to the aluminum stringers and bonded to the hull with spot welds or sealer. All of them are still secure, so what ever they used, it worked. Most of the pits are along the keel near the back, and there's two in the transom. The area where the transom sits inside of the main hull looks like it's soldered or packed with a softer metal, looks like lead, but lead wouldn't bond to aluminum. It's in that metal that theres a few perforated spots. But like I said they are so tiny that they can only be seen with a bright light. They didn't leak when in the water for some reason, at least not enough that I noticed it in the hour I let it sit and float in the lake down the road.
I wasn't sure what condition is was really in as far as leaks, so when I did test it, I backed the trailer in, left the boat tethered, and let it float there with some weight in it for about an hour. I wanted to see if there was maybe any problems that I couldn't see around the keel or hidden beneath the stringers. The only leak I saw was at a make shift plug I had made out of wood, silicon and washers to plug a below the water line through the hull fiting that was broken off.

Any ideas as to age by looking at this? I have searched the web for other DuraCraft boats, but none are like this, I find many standard runabouts, and then it's all newer bass boats. This is sort of a cross between the two. Its got a mid level wood deck with some floor storage, and four gunwale storage bins, and the forward bow storage. They left no real room for the battery or fuel tank at the rear.
I am probably going to put a 20 gallon tank up front and the maybe the battery too. That depends on which motor I use.
I'd like to reinforce the transom and build in an outboard tray and support so I could run a 50 HP or so, if not I'll be limited to about a 30 HP max. The bolt pattern drilled in the transom now matches a 25-30 HP Evinrude. The hull is surprisingly heavy, I can barely lift one end on the trailer, and there's nothing in it other than the forward floor section in the bow, and the tiller assembly.

Re: Aluminum boat - Saltwater corrosion repair

When you DO make the repairs to the hull, attach a good ground from the hull to the battery to help cut down on the galvanic corrosion that caused the holes to begin with.

Re: Aluminum boat - Saltwater corrosion repair

studlymandingo said:

When you DO make the repairs to the hull, attach a good ground from the hull to the battery to help cut down on the galvanic corrosion that caused the holes to begin with.

Click to expand...

That was my next question, I've been told both to ground and not to ground the hull, and I had one aluminum boat that was positive grounded.

This had no battery to ground before, the motor was magneto start aircooled, and there were no lights or any accessories ever installed, It had a hand pump to fill the livewell, and a hand bilge pump.
The anchor that was in it was a bit big though, it had a 30lb fluke type anchor and 200' of rope stored in the floor compartment. I guess the old owner really trusted this boat, the rope was only sun dried or faded at the very last few feet or so. The livewell is a partitioned off half of the right side storage box, I am trying to figure out if the boxes orgininally had lids of covers, I don't see any sign of any hardware. The cables all ran exposed on the right side, they run thru spring like eyes that are attached to the outside of the right storage box. The stick steer set up is mounted inside the left side box, but only the handle protrudes through a slot. The box was built around that set up, so I can say that was original. I would have to fill that slot inorder to make a clean install of an EZ glide system. (The last one I had with the EZ system was surface mounted). Surface mounting the steering would free up a rod box but ad another exposed cable. I'd rather find a way to flush mount the motor controls too.
The boat has a 66" beam width, so it's wide enough to move around compared to may 14" aluminum hulls, and I really like the lines and the hull design. If it were a complete open bow, I'd probably lean towards a forward platform, but the bow plate on this is structural. I will may do a different seat configuration than the twin pedestals it has, maybe a pedastal captains chair and rear bench with a removable second pedestal? I'd like to make it capable of fishing for three if I can. It also has some crude looking top frame that I have not yet figured out, it looks like it mounts to the rails somehow, and it weighs at least 100lbs. I've been told that they made these as late a the early 70's but I have never seen some of the equipment that this has on anything that late?
The steering stick and cable system is pretty old looking, and the pulleys are stainless steel with hard plastic pulleywheels, the Evinrude controler is a twin stick version with no electronics, and looks to have been disonnected for some time. The old owner was running a small Eskin Air cooled.
The seats are transplanted Pompanette captains chairs that are in good shape but too heavy for this boat. I will transplant those into my other boat. Someone recovered the last layer of plywood with some very early kitchen floor vinyl, looks like 1960s type stuff, its tar paper backed and light and dark green to match the outer paint. It breaks like glass when bent and it's made up of a four layers, the felt paper backing, the color layer, a metalic layer, then a thick clear layer.

The fuel tank that was with it said Firestone, and was pretty rough, it had the fittings for the Eskin motor. He also gave me an early Evinrude tank that he said was for the original motor. He had an old BIg twin there, but there's no way this held that motor.
The transom measures 20" and is full height with the gunwales with no dip or pan at the rear.
The dock bumper rail is extruded aluminum and is anodized and is in really nice shape. The hull also looks either powder coated or something, the paint lines cannot be felt and the paint is super thin but covers well. The one thing that really got me was that the ribs blocked the bilge from draining, the drain holes through each rib were up about 4 inches on each side of dead low center. That would allow the bilge to accumulate a few gallons of water before it drained to the rear and out from under the wood floor. I have drilled it through at the bottom so that any water in the hull goes directly to the rear. I can't imagine why they would build any boat like that, but it looked intentional. My concern was that any trapped water could freeze over the winter and cause expansion damage. The old owner stored it in the water but flipped it for the winter under his house that sat on stilts in the marsh.

I was reading somewhere online that Duracraft was the first company to come out with a one piece stamped hull, with no facets or seams. Apparently that technology was their claim to fame? This is the only DuraCraft I've seen other than a few 50's runabouts.
Does anyone else have any info on DuraCraft?