Hull Pitting and Patches - How concerned should I be?

[Sam_TG]

Hello everyone,

I'm looking to purchase a steel motor cruiser (1976) but am a little concerned about the condition of the hull from images provided. They aren't the best, but I'm trying to assess whether its even worth spending money on an out of water survey due to the cost of the work I may need to do.

You'll see she's a little odd in places (rudder shape, triple engines, Y brackets). My understanding is she was customised and designed by the current owner to cruise in European Canals as well as the open ocean.

Clearly an experienced surveyor needs to do some NDT and thickness measuring to properly understand what's going on, but I wanted some experienced eyes to give their 2cents before I started to spend money.

In Image 1 you'll see obvious pitting and patches on the hull. They look deep to me. If you squint you can see other signs of less deep galvanic corrosion elsewhere. The extent of the situation is unknown, but it looks wide-spread at a low level, and deep in a small area.

Image 2 and 3 give a little more detail of the hull and I cant see any signs of corrosion. There don't appear to be a significant number of zincs - could this be the reason for the corrosion?

To me, those pits look deep and the fact that there are patches already suggests the hull is not in an overall excellent state. What sort of work do you think I'd need to do and how extensive would you assess it to be?

I haven't got images showing the condition in the bilges and internal pictures don't show any obvious signs of corrosion (including engine room) so clearly I will need to look at these in person.

From what I've shared is there anything that makes you think I could be inheriting a hull with expensive (over $50,000) work to do?

Thanks

[neilpride]

Pic number 1: fresh sandblasting?

How thick its the bottom?

You make a UT in the hull?

1976, You may need to cut and weld plates, or patch the deep spots, and fill fair the lows.

3 zinc anodes in the keel, but i don't see any pitting in the keel, maybe need extra anodes in the bottom plates?

[Sam_TG]

Thanks for the feedback.

Originally Posted by neilpride

How thick its the bottom?

From the limited details I have, 6mm.

Originally Posted by neilpride

Pic number 1: fresh sandblasting?

Yes I believe so.

Originally Posted by neilpride

1976, You may need to cut and weld plates, or patch the deep spots, and fill fair the lows.

3 zinc anodes in the keel, but i don't see any pitting in the keel, maybe need extra anodes in the bottom plates?

Sounds like your assessment is similar to mine. Likely a "how long is a piece of string" question, but any sense of what it might cost to get it done professionally?

Agreed, I think it needs more zinc on the bottom plates.

I also want to check if the hull is being used as a negative return or has any current running through it. I don't have any information on that either - yet.

[Drunkonwatch]

Forget the outside spent half my life welding steel crab boats up in Alaska. Go inside repost pics the corrosion will be worse inside than out. If the inside is clean it might be that the alloy used was not marine grade lots of steel especially older will be susceptible to galvanic degradation.

[Ballsnall]

Originally Posted by Sam_TG

Clearly an experienced surveyor needs to do some NDT and thickness measuring to properly understand what's going on, but I wanted some experienced eyes to give their 2cents before I started to spend money.

NDT testing will only tell you the general thickness of the plating, which will not be much changed from new.
You can buy a thickness tester for a few hundred dollars these days and check it yourself.

To me, those pits look deep and the fact that there are patches already suggests the hull is not in an overall excellent state. What sort of work do you think I'd need to do and how extensive would you assess it to be?

Your assessment is correct, the corrosion pockets will need pad welding to repair and possibly a few areas will need replacing. This is all very simple to learn and do yourself if so inclined but would be very expensive to pay someone due to the amount of hours involved.

The main criteria to look for is what condition the inside of the hull is in and also what is the access like.
If it's in good condition inside with good access then the repairs are not that big a deal, just time consuming.

I haven't got images showing the condition in the bilges and internal pictures don't show any obvious signs of corrosion (including engine room) so clearly I will need to look at these in person.

From what I've shared is there anything that makes you think I could be inheriting a hull with expensive (over $50,000) work to do?
Thanks

Probably a week's work with a mig welder based on the photos and that would include removing the patches and repairing properly, two weeks tops but you will probably find other areas after a good inspection.

if your not hands on then probably best to walk away.

[Sam_TG]

Originally Posted by Drunkonwatch

Forget the outside spent half my life welding steel crab boats up in Alaska. Go inside repost pics the corrosion will be worse inside than out. If the inside is clean it might be that the alloy used was not marine grade lots of steel especially older will be susceptible to galvanic degradation.

I'll do that - thanks.

Really useful point on the marine grade steel too. I've added that to my list of questions to ask.

[Sam_TG]

Originally Posted by Ballsnall

Your assessment is correct, the corrosion pockets will need pad welding to repair and possibly a few areas will need replacing. This is all very simple to learn and do yourself if so inclined but would be very expensive to pay someone due to the amount of hours involved.

The main criteria to look for is what condition the inside of the hull is in and also what is the access like.
If it's in good condition inside with good access then the repairs are not that big a deal, just time consuming.

Probably a week's work with a mig welder based on the photos and that would include removing the patches and repairing properly, two weeks tops but you will probably find other areas after a good inspection.

if your not hands on then probably best to walk away.

I don't mind getting my hands dirty, but I'd also be the first to admit my ignorance. Thankfully my neighbour restores steel boats for a living so I plan to lean on him where I can.

My key takeaways from what you've said are:

• It may not be as bad as I feared (depending on the interior condition).
  
• Looking around 2+ weeks of work after a proper out of water inspection.
  
• Not bank breaking if done myself.
  
• That said - if I was to get someone to do it, any rough idea on the cost? You've said very expensive.. what was the figure range you had in mind when you said that?

Thinking about where that corrosion is, it could potentially involve removing ballast so potentially more complex but not significantly game-altering.

[thinwater]

Originally Posted by Ballsnall

NDT testing will only tell you the general thickness of the plating, which will not be much changed from new.
You can buy a thickness tester for a few hundred dollars these days and check it yourself....

You'll need a pit gauge to estimate the depth of the pits (eyeballing it is inaccurate).



(I've done a lot of oil tank inspection as a licensed professional. That looks like a LOT of repairs. Obviously, internal inspection is vital. The external work is straight forward for a professional welder, but the internals work could be inaccessible and difficult.)


I can weld and I would walk on by. They should have repaired the hull before offering it for sale.

[boatpoker]

Originally Posted by thinwater

You'll need a pit gauge to estimate the depth of the pits (eyeballing it is inaccurate).



(I've done a lot of oil tank inspection as a licensed professional. That looks like a LOT of repairs. Obviously, internal inspection is vital. The external work is straight forward for a professional welder, but the internals work could be inaccessible and difficult.)


I can weld and I would walk on by. They should have repaired the hull before offering it for sale.

This ^^^