Boat Corrosion

[Hunter24]

So I bought this boat a couple of years ago. It is a 2000 Starcraft starfire 190. After the first year I noticed paint blistering and thought nothing of it. Ended up after cleaning it up there was several pin holes. I believe it was a mixture between the foam inside and he had some things grounded to the boat. This is and was strictly a fresh water boat. Just curious if anyone has seen this before and what my options would be? I don’t really want to rip apart everything inside just to find out no one can do anything about it. It mainly seems to be on the starboard side at the back right at the water line. The metal transom is bad too. But I am figuring it has to maybe do with the wood from factory. Really like this boat don’t really want to just get rid of it I would really like to fix it. Temporarily fixed it with epoxy on the outside. Seems to be holding but i know not fixing it it is probably just getting worse on the inside.

 

[DaleH]

Well, I've seen worse, like the hull in my signature - "16' Starcraft NEW Transom Skins" that looked like it got shot multiple times with 00 buck from a shotgun.

Let me ask 1st, do you keep this on atrailer or is it moored or docked in the water? Also remove any bonding to the hull the PO did. Go back to the battery or to an Ancor brand 'Power Post' (acts like a remote ground, but is cabled to your battery negative post).

Here's what I would do ... but dependent on your answer above, I might add other suggestions.

1. Remove anything and EVERYTHING off the tin panels where you now see any evidence of corrosion
2. Ensure you remove any 'white' corrosion in the holes, then sand inside with agressive NEW 60 to 8- grit metal paper
3. Wipe area well with white vinegar, then clean cloth with water on it - let dry
4. Place duck tape on 'outside' of hull over hole
5. Mix up West Systems G-Flex 650 (only $22 a kit) as it is a FLEXIBLE epoxy and fill the hole. You want a LARGE plug or blob of goop on the inside. You 'may' need to tip the hull sideways so as to keep the epoxy on the hole as it cures.Or keep wiping it back onto the reapir area. If you had cabosil fibers on hand, you couldthicken it somewhat or wait a tad until it begins to 'kick'. You can mix it reliably in tiny amounts (2 to 1 mix). I myself would not use a hard epoxy like JB Weld here ...
6. When cured, remove tape (naptha or gas is your friend here, to remove any adhesive) and see how flush it is. If needed, skim coat a coat from the outside, but tape off surrounding area well, to within 1/4" or so of repair/hole
7. Once satisfied, sand outside flush, multiple grits, and paint. Any bare tin should also be prepped with white vinegar (it etches aluminum), then rinsed and prime with aluminum primer when dry, multiple light/thin coats better than one globby thick one ...
8. Paint as needed, I recommend Rust-Oleum regular enamal or their hard 'topside' paint version (darn hard, glossy finish!)

Go enjoy the boat ... and just keep an eye on it.

If you have other questions, ask away and SHOW pictures as needed.

FWIW I've seen this on Starcafts of mid-90s to later vintage, (mine was a '96) believe it how the wood was or wasn't treated, if there's wood against those surfaces affected.

 

[Hunter24]

I keep it on a trailer but he had a boat house and that is where it lived. He owned a cottage and he always had it in there.
I also re did his wiring and grounded everything to the battery and added a marine grade shut off for the battery.

And thank you for your suggestions it is highly appreciated. I guess my biggest concern is getting to the effected area to fix it. Not to sure how easy the interior is going to come out or if it will be blocked by other plates underneath.

I also know I have some leaking rivets. I hope it isn’t from corrosion too. What would be my best bet for that? Go around and rebuck them all?

Also should I put the foam back in when I take it out or would it be better not to put new stuff in?

 

[DaleH]

I also know I have some leaking rivets. I hope it isn’t from corrosion too. What would be my best bet for that? Go around and rebuck them all?

IMHO, for NON-saltwater boats, most loose rivets come from 'wet' hulls and freezing temperatures causing the rivets to be stressed over time, recall ice expands where water changes state from water to ice. I've seen 40-year old tin hulls used in saltwater to boot, that ate stored upside-down when out of the water, all cold NE Winter long ... and they don't leak a drop.

Otherwise loose rivets from use, or abuse (hitting a ton of wakes at speed) or use like trailering a tin hull at 70MPH, on hard asphalt roads, on a poorly supported trailer is one sure way to loosen them up, LOL!

Yes, rebuck them IF you can get access to both sides. Else best to make waterproof from the outside. You can coat each or suspect rivet head with that G-Flex 650 or coat the entire hull (part immersed inwater) with Steel-Flex.

Also should I put the foam back in when I take it out or would it be better not to put new stuff in?

Depends, I'd re-use if could guaranteee it is 'dry'. Otherwise closed-cell insulation foam boards or even cheap pool noodles work, especially for a trailered boat.

 

[Hunter24]

Okay that makes sense. Especially if the foam is soaked he had it in an un-heated boat house and winters get pretty bad here. So I can see where that would happen.

And also what would your opinion be as to why it started doing this is such a weird place? Mixture of the wood, foam and electrolysis?

Just still debating if it’s worth the time or time for a different boat

 

[Hunter24]

Was scrolling through my phone the other day and found (bad quality) pictures of what those spots looked like before I realized what they were. And when I started to think about it a bit more I remembered that some of the blistering when cleaned off looked okay but had a very small indent (size of the tip of a pick) and didn’t make a hole. It is making me wonder now if these corrosion spots possibly started from the outside? If it started from the inside wouldnt all of those effected areas be a hole?? And what could cause it to start from the outside like that? Just curious.

 

[sonny.barile]

Was scrolling through my phone the other day and found (bad quality) pictures of what those spots looked like before I realized what they were. And when I started to think about it a bit more I remembered that some of the blistering when cleaned off looked okay but had a very small indent (size of the tip of a pick) and didn’t make a hole. It is making me wonder now if these corrosion spots possibly started from the outside? If it started from the inside wouldnt all of those effected areas be a hole?? And what could cause it to start from the outside like that? Just curious.

Did you ever get to the bottom of this?

 

[Hunter24]

Unfortunately this winter didn’t allow any time to rip the boat apart. I am hoping to at least get enough off and drill a small hole from the inside to see what’s going on.

 

[DaleH]

It is making me wonder now if these corrosion spots possibly started from the outside? If it started from the inside wouldnt all of those effected areas be a hole?? And what could cause it to start from the outside like that? Just curious.

Is it paint? IF paint ... and IF a copper-based anti-fouling paint ... then yes, that could cause corrosive attacks.

 

[Hunter24]

Is it paint? IF paint ... and IF a copper-based anti-fouling paint ... then yes, that could cause corrosive attacks.

It shouldn’t be the paint, as far as I know it is factory paint. 2 spots that I have “fixed” with epoxy started to come loose so I pulled them off and the holes got a little bigger (barely) and again the white corrosive spots were from the outside. Hopefully this week I will have time to at least drill that inspection hole from the inside and see how bad it is. Another issue I started having that’s getting worse Is a lot of loose rivets and only on the starboard side of the boat.

 

[thill]

IF it has bottom paint and it's the wrong kind it sure could cause that.

But it could be that the factory paint got corrosion under it, and it's eating away under there. Do you see any blistering paint on that side?

 

[airshot]

almost sounds like electrolysis from the hull being used as a ground.

 

[Hunter24]

Well I finally had a chance to cut a hole rip some foam out and see what’s going on…this is the biggest hole in the boat (size of a pencil eraser) no where near as bad as I thought it was going to be…from all of the other boats I have seen on these forums it is usually peppered with corrosion. This is only one hole out of a few on the side, not including the loose rivets. Foam was wet but nothing crazy…isn’t broke down at all was still very much intact so idk what’s going on here…I figured if it was caused by wet foam but I thought the foam would at least be soaking wet and broke down if that was the case?? Any thoughts now?

 

[thill]

That looks like a puncture, or maybe a bolt hole. Hard to say.

Lock in a short bolt, nut, 2 washers and sealant and don't worry about it too much.

I had a customer who had a couple of similar holes, and he went crazy trying to get it welded. Spent nights awake worrying about it and so on. I showed him the bolt trick, and he started laughing and went fishing and forgot all about it.

 

[Hunter24]

almost sounds like electrolysis from the hull being used as a ground.

What would be some good tests to confirm this? He did have ground going to the hull which I switched it to go directly to the battery. The only thing I don’t understand is you will always have a ground going to the hull would you not? The engine is naturally going to ground it? Thanks

 

[airshot]

Nope, not an electrician here but I do know that grounding the hull will cause electrollosis and eat away at the boat, ground goes directly to neg post on battery not the hull.

 

[thill]

What would be some good tests to confirm this? He did have ground going to the hull which I switched it to go directly to the battery. The only thing I don’t understand is you will always have a ground going to the hull would you not? The engine is naturally going to ground it? Thanks

There it is.

Yes, the boat will be grounded via the motor, but for the electrical system, you want everything going directly to the battery, not going through the hull primarily.

I have had very good success using solid rivets, short bolts and JB Weld in spots like that.

I recently had a boat with a bunch of bad corrosion spots on the transom:



This was a lot of damage to epoxy, and I ended up using a MIG welder and a bottle of Argon gas, and I welded them all closed. Used a flap disc to smooth the welds out, touched up spots and then primed and painted:



Obviously, I'm pleased with the results.

Now that you have founded the reason for the electrolysis, you could JB weld, rivet or bolt the spots. Rivets or bolts will definitely hold, but may not look good, if they stand out. JB weld might hold well for you, if you prep it well. If not, you may want to find someone who can TIG or MIG the spots.

 

[Hunter24]

Had someone attempt to weld the one spot. Let’s just say he didn’t make it bigger but it definitely didn’t seal all the way. That’s the least of my worry’s tho. It seems like every year I take the boat up north and use it for a week (sits in the water all week) I pull it out and there is more and more little spots where corrosion starts to show. As previously stated all grounds go directly to the battery. I don’t understand what could continue to make this worst and worst every year. I would understand if it was the same spots getting bigger but it’s new spots that flake the paint and have that white chalk. The one is actually not too nice and it was only in the water for a week.

 

[thill]

Sometimes, boats didn't get a good primer coat.

Or someone wanted to paint the boat and decided to strip the original paint and primer down to bare metal. They didn't use a good primer, and so water gets under the paint and causes corrosion.

Sorry that you are having that issue.