Pitted, rusting fuel tank

[Faith]

I had a survey done on a 2008 Mainship 34 Pilot II and the surveyor snapped a photo of a fuel tank with pits and rust on it. How big of a deal is this? He recommended that the buyer remove the 2 Yanmar diesels and find a new fuel tank which would be dificult because Mainship is ourt of business. Other people said it's not that big of a deal and would cost about 4 k for the tank, not sure about the labor (much more $ I'm sure). Surveyor said to me privately, if it was his boat he'd put some type of coating over it and monitor it.

Any thoughts or recommendations? Trying to get a replacement cost mainly. Thank you!

Thanks!

 

[sean9c]

Looking at the weld in the corner of the pic that sure looks like aluminum. Are you sure it's even steel? Take a magnet to it. Maybe that's just some sort of staining

 

[O C Diver]

Looking at the weld in the corner of the pic that sure looks like aluminum. Are you sure it's even steel? Take a magnet to it. Maybe that's just some sort of staining

Good catch! I'm very surprised a 2008 recreational boat built in the USA would have a steel tank.

Ted

 

[rslifkin]

I agree, that's likely an aluminum tank. Not sure what the staining is from, but the pitting warrants a close inspection in my eyes.

 

[Faith]

I agree, that's likely an aluminum tank. Not sure what the staining is from, but the pitting warrants a close inspection in my eyes.

What would cause the pitting?

 

[Faith]

It is an aluminum Tank.

 

[tiltrider1]

If I was the seller I would say take it or leave it. If I was the buyer I would monitor. If this bothers some one I would remove the tank wire wheel it and coat it with epoxy.

That said, I am going solely off the pictures posted. In the real world I might see something that leads me to believe things are much worse where I am un able to see. In that case the surveyor might be correct.

Aluminum tanks almost always corrode from the outside in and if caught early enough are easily repaired with an epoxy patch.

 

[tiltrider1]

As to what is causing this. Most likely rain water leaks running down the back side of the tank.

 

[Faith]

If I was the seller I would say take it or leave it. If I was the buyer I would monitor. If this bothers some one I would remove the tank wire wheel it and coat it with epoxy.

That said, I am going solely off the pictures posted. In the real world I might see something that leads me to believe things are much worse where I am un able to see. In that case the surveyor might be correct.

Aluminum tanks almost always corrode from the outside in and if caught early enough are easily repaired with an epoxy patch.

Thank you for your advice, Appreciate it.

 

[Max1]

I wish my tanks looked that good!.

Sanding wheel, then Tremclad. (White)

That us exactly what I am doing to my steel tanks at this very moment.

 

[Comodave]

That is an aluminum tank. Don’t know exactly what the discoloration is though. As said above check it with a magnet to confirm it. Surprised that the surveyor didn’t know what it was or have a magnet with him/her to verify it.

As to cost it could be about $4K for a new tank. The labor is the big unknown. It could easily be $5 to $6K for labor. Unless you DIY it. Lots of grunt work. But not too technical.

You don’t need Mainship to get a new tank. You would have one custom made to fit. That is the normal procedure. The surveyor should know that.

 

[Faith]

That is an aluminum tank. Don’t know exactly what the discoloration is though. As said above check it with a magnet to confirm it. Surprised that the surveyor didn’t know what it was or have a magnet with him/her to verify it.

As to cost it could be about $4K for a new tank. The labor is the big unknown. It could easily be $5 to $6K for labor. Unless you DIY it. Lots of grunt work. But not too technical.

You don’t need Mainship to get a new tank. You would have one custom made to fit. That is the normal procedure. The surveyor should know that.

Thank you, lots of helpful info.

 

[sunchaser]

Thank you, lots of helpful info.

That could be dissimilar metal corrosion. If so, determining the cause is important to prevent any further issues.

 

[Iggy]

I would clean it first and take another pic. There looks like one big scratch vs pitting. Maybe we are looking at scratches along with some form of dirt?

 

[Southern Boater]

Could the rust be related to steel filings being “flung” onto the tank, from somebody using a grinder (in the past) then external condensation from the fuel tank mixed with vented salt air create the rust, or salt water mist from a leaking shaft packing gland?
Perhaps splatter from a failed exhaust elbow?

Assuming this is an alloy tank.

 

[sean9c]

Maybe it was strapped down with steel straps. Whatever it was it got water under it and started corroding. Keep everything dry and it won't be a problem.

 

[RT Firefly]

Greetings,
Welcome aboard. Ms. F. As others have said...Clean it off really well, THEN you might have a better idea of cause, extent of pitting. Since you don't own the boat it may not be possible.

Just looked and guessed: If this is the Mainship 34 Eufloria @129K. Get the seller to fix it or offer $20K less.
Edit:
Also noticed in the Eufloria listing, no ER pictures. Failure if a broker to include at least one picture of the machinery spaces immediately kills any interest I might have in that boat.

 

[Comodave]

I didn’t look at the listing but if there are no engine room photos I always wonder why not? Are they trying to hide something or just a lazy broker???

 

[Faith]

Greetings,
Welcome aboard. Ms. F. As others have said...Clean it off really well, THEN you might have a better idea of cause, extent of pitting. Since you don't own the boat it may not be possible.

Just looked and guessed: If this is the Mainship 34 Eufloria @129K. Get the seller to fix it or offer $20K less.
Edit:
Also noticed in the Eufloria listing, no ER pictures. Failure if a broker to include at least one picture of the machinery spaces immediately kills any interest I might have in that boat.

Au Contraire, we just reduced the Ask by 20k this week, and there's an entire, thorough 18 minute+ video that shows the entire boat including the twin Yammars which are pretty accessible, did you not see that?

 

[Faith]

I didn’t look at the listing but if there are no engine room photos I always wonder why not? Are they trying to hide something or just a lazy broker???

Neither. There's a complete video showing the twin yanmars, etc.

 

[Comodave]

Neither. There's a complete video showing the twin yanmars, etc.

Ok, that is good.

 

[RT Firefly]

Greetings,
Nope. Can't find video.

 

[jleonard]

IF you decide to paint/coat the tank, check out The Eastwood company. I used their sealer kit on my steel tanks a few years ago. It worked and looked great. You would have to ask them if it would work on aluminum or if they have a kit for aluminum.

 

[Marco Flamingo]

Is the condition uniform around the tank or concentrated on the bottom? If it is the result of water or other contaminants sitting in a particular area, I would seriously consider an epoxy coating of that area. While difficult to predict exactly, if it took 15 years to get to that condition on the tank bottom (for instance), then with that area sealed up with epoxy, it would take another 40 years for the condition to cause serious damage to the other areas (assuming no additional care is taken to avoid whatever caused the original pitting).

I had a tank bottom coated and partial epoxy coating of the sides in a steel tank without removing the engine to pull the tank. Cost was $2,000 to hire out the fix. It took one day, including adding 3 inspection ports and the disposal of the goop in the bottom of the tank that cause the leak. Given that the sides, baffles, and top of my 40 year-old tanks were still in great shape, I can figure that the tanks will last at least another 80 years.

It could be a DIY project, especially with an aluminum tank. For steel, a 8" hole saw is over $100, as is each port. Aluminum can be cut with a $50 hole saw, but having it done "professionally" seemed like money well spent. When I called a year later to get the other tank done as a prophylactic measure, he was so busy I haven't been able to get an appointment. Could also be that his price has increased as it does seem to be a bargain.

 

[NWpilot]

In the video it appears the tank lies across the beam of the boat and access to it is limited. It also appears that taking it out would be a major operation and possibly involve removing the engines. For these reasons I would be concerned about the pitting. If you really want the boat I would ask the the owner for permission to have someone with experience on aluminum tank take a look at it.
Aluminum is subject to electrolysis and my guess is that's what is causing the pitting so you need to find the source. Normally it happens when the tank contacts water. I don't see any way to get access to the bottom, ends or the far side of the tank to apply a coating.
I just removed my 110 gal. tank due to pitting and a leak (it's 45 years old) and I'm having a new one built for $2,500.

 

[Bmarler]

Is the condition uniform around the tank or concentrated on the bottom? If it is the result of water or other contaminants sitting in a particular area, I would seriously consider an epoxy coating of that area. While difficult to predict exactly, if it took 15 years to get to that condition on the tank bottom (for instance), then with that area sealed up with epoxy, it would take another 40 years for the condition to cause serious damage to the other areas (assuming no additional care is taken to avoid whatever caused the original pitting).

I had a tank bottom coated and partial epoxy coating of the sides in a steel tank without removing the engine to pull the tank. Cost was $2,000 to hire out the fix. It took one day, including adding 3 inspection ports and the disposal of the goop in the bottom of the tank that cause the leak. Given that the sides, baffles, and top of my 40 year-old tanks were still in great shape, I can figure that the tanks will last at least another 80 years.

It could be a DIY project, especially with an aluminum tank. For steel, a 8" hole saw is over $100, as is each port. Aluminum can be cut with a $50 hole saw, but having it done "professionally" seemed like money well spent. When I called a year later to get the other tank done as a prophylactic measure, he was so busy I haven't been able to get an appointment. Could also be that his price has increased as it does seem to be a bargain.

I think that outfit works like a triage system, if you’re leaking you get to the front of the line.
I can tell you though, it’s about three times what you previously paid to have it done now.

 

[BDalt]

Coming late to this post but I've 2 cents to add that did not seem to come up. The survey is relevant to the negotiations but also eventually for insurance purposes. The risk analysis of the insurer may lead to a conditional quote, or outright decline. Regarding the coating suggestion, it was not made in the survey, only as an aside. For aluminum tanks there is a divide between manufacturers, one advertises epoxy coating comes with the tank as standard, another won't coat a tank and stands by the natural oxidation of the aluminum as proper protection. The logic being that any inevitable nicks in a coating will end up trapping moisture and promoting corrosion. I buy into that logic. The pitting evident on the tank surface is hard to explain and has me thinking the photo is so zoomed in so much as to exaggerate the "pits". The scale is sort of revealed by the weld in evidence, appearing huge and which is also pristine. Corroding aluminum is not rusty, so the discoloration is something else. The pitting, maybe just poor quality original stock? In a post on a different forum I asked if my steel tanks were gonners. Many opinions there and suggestions for pressure testing to assess risk of failure. My new aluminum tanks are expected shortly, and the cost is above what has been suggested in other posts in this thread.