Help me decide the best way to fix pitting

[yeti meat]

Hi Guys,
Im new here,

So I have a question for you guys.
I have a 80's lund that a former owner put treated plywood down as a floor. Brilliant. The plywood looks just as good as it did they day they installed it Im sure.
However as you can probably guess... the bottom of the boat looks pretty bad. I have stripped down the floor to assess the situation. As far as I can tell, no holes go all the way through, however Once I strip the bottom, Im going to assume a few of them do.

So, Im in remote AK.
everything is hard to get here, and you kinda have to make due with what you have.
Ive scoured the internet looking for an affordable fix.

Ive come across G flex 655 as a solution to fixing my transom issues (which are worse).
Im wondering if I could also use that to spot fill these pits in the floor, after using vinegar and zinc chromate primer? Or would jb marine be a better option?
Or is there perhaps a better option Im ignorant of?

Im determined to make this thing work for at least a couple years till I can find a boat in better condition.
Thanks for the help
Cheers

 

[yeti meat]

Back again with more data, and a plan…


Soooo.
After assessing the bottom of the boat I have determined that this roughly 48” x 36” section is compromised.

Spot filling is futile.

Better to do a large bandaid approach.


So My plan is to

1. remove all the rivets in this area.

2. Clean the area inside and ospho it.

3. Just drill out the larger corroded holes with a step bit. I figure the largest holes will end up being maybe 3/8” -1/2”.

4 .Glue with g flex 655, and (temporarily screwing) some pieces of 5052 down on the inside.

Id screw through the existing rivet holes from the ouside through the 5052 and into some plywood. This should suck it down pretty tight.

Once its dried, Ill remove the screws, and plywood, and drill out the holes to the proper size.

5. Reinstall the rivets.


This should restore the integrity of the floor and seal it pretty well.


But Im left with a Buch of 3/8 holes in the bottom of the boat. Lets say 20 of them.


Just need help nailing down what to fill the holes on the bottom with. Im guessing jb weld ( cheapest) Marine Tex , splash zone? Or is there a better option?


I think I have a free source for the donor metal. So the only costs to do this are rivets and epoxy basically.

Should be around $50



Yeah I know its going to be a floating abortion. Believe me it makes me ill to think about it.

Im a metal fabricator. But I dont have access to the right tools or a shop out here, so gotta use what’s available and make it work somehow, and make it reliable.



Ok so critique away at my plan and tell me what you think would be the best hole filler for the post op bottom.



Thanks for the help, from a little island in AK

Cheers

 

[Zip]

Gflex 650k seems to be popular. I would use it on freshly cleaned bare aluminum however, not over the zinc primer. I read on another forum, that the acidity in the primer along with the acidity in the epoxy create bonding problems, but I dont have first hand experience. I have a lot of pitting and holes, plan to use 650k, and the larger holes and areas - I am going to rivet a new aluminum/fiberglass sandwich method. And my boat looks a lot worse than yours!

 

[LDUBS]

I see where some guys riveting a patch on use two patches, inside and out with their sealant of choice buttered on both. If you are going to use one, is it better to put it on the inside or outside? I don't know the answer or if it makes a difference.

 

[Lost But Happy]

Gray marine tex kicks a$$.

 

[yeti meat]

Gflex 650k seems to be popular. I would use it on freshly cleaned bare aluminum however, not over the zinc primer. I read on another forum, that the acidity in the primer along with the acidity in the epoxy create bonding problems, but I dont have first hand experience. I have a lot of pitting and holes, plan to use 650k, and the larger holes and areas - I am going to rivet a new aluminum/fiberglass sandwich method. And my boat looks a lot worse than yours!

Thanks for the response, and the tip about the primer. That could have been a costly mistake..
Sorry to hear you have a similar/ worse problem.
So 650 sandwich on clean aluminum. That would answer the what to fill the holes with question... Im contemplating wether or not to that as well. hmmm
Thanks Zip!

 

[yeti meat]

Gray marine tex kicks a$$.

View attachment 117849

Thanks for the Marine Tex vote. seems pretty easy and foolproof

 

[yeti meat]

I see where some guys riveting a patch on use two patches, inside and out with their sealant of choice buttered on both. If you are going to use one, is it better to put it on the inside or outside? I don't know the answer or if it makes a difference.

Thanks for the response. I see what you mean. Just use the one product in between 2 pieces.

I was thinking it would be easier to patch the inside as there are no ribs or anything in the way, and thats where the majority of the corrosion is. I could do la couple large 2'x3' patches.
The outside doesn't look too bad so it would just be a few dozen smallish holes. Id also have to do smaller patches that dont cover what's under the ribs.

That said depending on how much aluminum I can scrounge up, perhaps Ill do the outside too. Or use the fiber glass as mentioned below.

Thanks very much

 

[mirrocraft16]

I had an 80's Bass Tracker that was badly corroded along both sides where it sat on the bunks. The former owner used it for crabbing and it sat on salt soaked bunk carpet full time. After replacing the bunks and carpet, I scrubbed the hull to get a better look and decided the only way to get the corrosion completely off the metal was to lightly bead blast it. I went over the area with glass beads in a hand held gun at lower pressure a few areas got worse but that meant they needed to be fixed either way.
I didn't want to do any metal patches as it would look terrible and no doubt they'd be catching the carpeted bunks every time I loaded the boat. I went with Marine Tex, applied like bondo on a squeegee. I sanded and painted the area and kept an eye on it.
It never gave me any issues and the current owner is still using the boat 30 years later.

I have noticed that some boats are just prone to corrosion. I've had a few that no matter what they would get surface corrosion all over, regardless of what I did to stop it or where it was used.
My two Grumman boats and one Duratech were both like that. The Duratech would get white corrosion all over it just sitting under the cover for a week. Nothing I did seemed to stop it or slow it down. After having a few spots corrode through the hull I fixed it with Marine Tex and sold it. One Sea Nymph and both Grumman boats both had perforation in the transom area but that was because they used pressure treated plywood from the factory. All three were OMC owned at the time they were built.
The older Grumman boats I had were great, they never corroded regardless but those were pre-OMC year models.

 

[Lost But Happy]

Thanks for the Marine Tex vote. seems pretty easy and foolproof

It is. Great to work with after it cures too. Just gotta watch your pot time. Need to mix it as close to the instructions as possible. DAMHIK lol

 

[Zip]

I had an 80's Bass Tracker that was badly corroded along both sides where it sat on the bunks. The former owner used it for crabbing and it sat on salt soaked bunk carpet full time. After replacing the bunks and carpet, I scrubbed the hull to get a better look and decided the only way to get the corrosion completely off the metal was to lightly bead blast it. I went over the area with glass beads in a hand held gun at lower pressure a few areas got worse but that meant they needed to be fixed either way.
I didn't want to do any metal patches as it would look terrible and no doubt they'd be catching the carpeted bunks every time I loaded the boat. I went with Marine Tex, applied like bondo on a squeegee. I sanded and painted the area and kept an eye on it.
It never gave me any issues and the current owner is still using the boat 30 years later.

I have noticed that some boats are just prone to corrosion. I've had a few that no matter what they would get surface corrosion all over, regardless of what I did to stop it or where it was used.
My two Grumman boats and one Duratech were both like that. The Duratech would get white corrosion all over it just sitting under the cover for a week. Nothing I did seemed to stop it or slow it down. After having a few spots corrode through the hull I fixed it with Marine Tex and sold it. One Sea Nymph and both Grumman boats both had perforation in the transom area but that was because they used pressure treated plywood from the factory. All three were OMC owned at the time they were built.
The older Grumman boats I had were great, they never corroded regardless but those were pre-OMC year models.

Well thats a bummer! I have a Grumman, any idea when OMC bought them? Mine is a 90. My transom was not pressure treated, but it was rotted. Previous owner half *** painted it with antifouling paint, and it lived in saltwater. When I got it there were huge blisters in the paint still holding salt that dried Every time I go to work on it - I have to ask myself, how far gone, is too far gone... But here I am still believing it could work. The 14GSS is SOOO wide and long its the perfect size for a 14fter I really want to make it work.

 

[LDUBS]

Thanks for the response. I see what you mean. Just use the one product in between 2 pieces.

I was thinking it would be easier to patch the inside as there are no ribs or anything in the way, and thats where the majority of the corrosion is. I could do la couple large 2'x3' patches.
The outside doesn't look too bad so it would just be a few dozen smallish holes. Id also have to do smaller patches that dont cover what's under the ribs.

That said depending on how much aluminum I can scrounge up, perhaps Ill do the outside too. Or use the fiber glass as mentioned below.

Thanks very much

I just realized you are talking about a 2x3 square foot patch! I was thinking inches. Lol. So you would be covering several thru holes with that large patch. I would be generous with whatever sealant it used and add rivets as needed. But, being a metal worker, you are going to know more about these things than me.

It will be great if you keep posting how you handle this.

 

[yeti meat]

I had an 80's Bass Tracker that was badly corroded along both sides where it sat on the bunks. The former owner used it for crabbing and it sat on salt soaked bunk carpet full time. After replacing the bunks and carpet, I scrubbed the hull to get a better look and decided the only way to get the corrosion completely off the metal was to lightly bead blast it. I went over the area with glass beads in a hand held gun at lower pressure a few areas got worse but that meant they needed to be fixed either way.
I didn't want to do any metal patches as it would look terrible and no doubt they'd be catching the carpeted bunks every time I loaded the boat. I went with Marine Tex, applied like bondo on a squeegee. I sanded and painted the area and kept an eye on it.
It never gave me any issues and the current owner is still using the boat 30 years later.

I have noticed that some boats are just prone to corrosion. I've had a few that no matter what they would get surface corrosion all over, regardless of what I did to stop it or where it was used.
My two Grumman boats and one Duratech were both like that. The Duratech would get white corrosion all over it just sitting under the cover for a week. Nothing I did seemed to stop it or slow it down. After having a few spots corrode through the hull I fixed it with Marine Tex and sold it. One Sea Nymph and both Grumman boats both had perforation in the transom area but that was because they used pressure treated plywood from the factory. All three were OMC owned at the time they were built.
The older Grumman boats I had were great, they never corroded regardless but those were pre-OMC year models.

Thanks for the sharing your experience with Marine Tex.
That is what I was thinking. squeegee it on like bondo. take care of a wide area in a hurry.
30 years and it still holding is proof enough for me..
That would be optimal and the easiest way for me to get those halibut in my freezer where they belong.
Do you remember what you painted it with by chance ?

Sounds like the boat manufacturers are using cheaper alloys for some of the hulls. which is why some deteriorate before your eyes.. It would be interesting to find out what the best alloys are. and what they used on the Grumman and the duratech.
I believe they used 5052 on this Lund and overall it seems in pretty good shape for being abused up here in the salt water.
Looks like 5000 series aluminum alloys are optimal. it would be interesting to find out real world which ones are the best, and which ones failed.

 

[yeti meat]

Well thats a bummer! I have a Grumman, any idea when OMC bought them? Mine is a 90. My transom was not pressure treated, but it was rotted. Previous owner half *** painted it with antifouling paint, and it lived in saltwater. When I got it there were huge blisters in the paint still holding salt that dried Every time I go to work on it - I have to ask myself, how far gone, is too far gone... But here I am still believing it could work. The 14GSS is SOOO wide and long its the perfect size for a 14fter I really want to make it work.

Not sure if you are aware, but some of those anti fouling paints have copper in them same as the pressure treat... if thats the case, then that is why your metal is jacked even though the transom was not treated.

 

[yeti meat]

I just realized you are talking about a 2x3 square foot patch! I was thinking inches. Lol. So you would be covering several thru holes with that large patch. I would be generous with whatever sealant it used and add rivets as needed. But, being a metal worker, you are going to know more about these things than me.

It will be great if you keep posting how you handle this.

Yeah, maybe 3’ x 4’ total.

I know enough about metal work to know that I know nothing..lol

Yeah Ill keep you guys updated on the fix.

It might be a multi stage thing. Ill try to do the most conservative thing first and see how that goes.


Maybe I should throw up the transom fix on here too.

Thats a horror show, but its above the water line, so a less critical fix.


I assume the same rocket surgeon that used pressure treat for the floor.. thought it would be a good idea to sandwich the transom in between two pieces of 1/4 metal…..with a nice piece of pressure treat between them….lol Sigh..

If nothing else it will be interesting to see how a fix with limited access to tools and materials goes.


Keep the critiques and suggestions coming.


I think Ill order some Marine Tex in case I decide to go that route first. I already have the g flex on the way.

 

[Zip]

Not sure if you are aware, but some of those anti fouling paints have copper in them same as the pressure treat... if thats the case, then that is why your metal is jacked even though the transom was not treated.

Absolutely could be the issue. There is a coating of epoxy under the paint but its in bad shape for sure. I was thinking marine tex for awhile but a post awhile back showed some serious corrosion under it when it was removed. Ill try and find it, thats why I plan to cover wide areas with fiberglass and 650k, then rivet a plate on.

EDIT: I believe it was 5200 that had some nasty pics NOT marinetex. Not really relevant since you specifically mention marintex. Either way heres the pic:

 

[yeti meat]

Absolutely could be the issue. There is a coating of epoxy under the paint but its in bad shape for sure. I was thinking marine tex for awhile but a post awhile back showed some serious corrosion under it when it was removed. Ill try and find it, thats why I plan to cover wide areas with fiberglass and 650k, then rivet a plate on.

EDIT: I believe it was 5200 that had some nasty pics NOT marinetex. Not really relevant since you specifically mention marintex. Either way heres the pic:
View attachment 117866

thanks for the pics. Please keep us updated on your patch.
Ive heard silicone has corrosive properties. Also any screws or bolts other than aluminum are going to instigate corrosion. Hard to say. I suppose every incident is unique. however if someone doesn't get all the corrosion out before putting on any kind of patch over it, the corrosion will just continue under the patch.

Might be shocking, but Im actually drilling oversize holes to remove all the corrosion before I move on to any patching or potential welding.

 

[yeti meat]

Update.
So starting from the outside of the boat Im addressing the corrosion that is present there.
As you can see once I hit it with a stainless wire cup the holes are apparent and you can see the blister in the middle of the material. in order to properly fix this you need to get to clean metal meaning unfortunately.. making the holes bigger.

Once I got all the outside corrosion taken care of, you can see what it looks like from the inside. leprosy..
Again, going from conservative to extreme, Im going to attempt to die grind out the blisters. currently waiting on aluminum burs to come. If I can get this stuff out with a bur, that would be gret

 

[Zip]

Wouldn't sanding to bare aluminum, and then an acid wash, quickly followed by some sort of barrier coat (gluvit or totalboat) prevent corrosion in the future? My understanding is that the acid literally eats all the corrosion away, and you got a few hours before aluminum oxide starts all over again. The idea of sandwiching corrosion is certainly something I have considered. But I believe a liquid acid on the pitting/corrosion will dissolve it completely no?

 

[yeti meat]

Wouldn't sanding to bare aluminum, and then an acid wash, quickly followed by some sort of barrier coat (gluvit or totalboat) prevent corrosion in the future? My understanding is that the acid literally eats all the corrosion away, and you got a few hours before aluminum oxide starts all over again. The idea of sandwiching corrosion is certainly something I have considered. But I believe a liquid acid on the pitting/corrosion will dissolve it completely no?

If you can get all the corrosion, it should work. However if your corrosion is like mine and is basically a blister, and the corrosion is actually hidden even though it appears that you got it all is when you might have a problem.

I tried using ospho on a spot to dissolve the corrosion on one of theses larger spots. I could see that it wasn't really getting it all. perhaps your acid wash will do a better job than mine. But for me, Im gonna need to expose it all with the die grinder and then do the acid wash. If it ends up not leaving enough material, Ill end up drilling it out.