Question
…I am looking for a used aluminum yacht…I have read all your articles on how to care for an aluminum yacht. However, how to look for serious problems on a used (25 years old) aluminum yacht?
I know that I can check the electrical installation with a meter, but can I find any alarming signs of electrolysis in a yacht that is in the water? Are there any other areas on a used aluminum yacht that I should pay attention to?
My question concerns hull corrosion and the resulting lower strength of the hull.
Thank you John for so detailed answer. I just ordered silver chloride reference cell.
And make sure the engine screws are A4 stainless and that an insulating agent like Ted gel is used so you won’t get corrosion between the screws and the access panel
Thanks. But that’s for later if I buy this boat. Corroded screws are not a deal breaker for me 😉
I would also recommend you also to check visually inside the water tanks.
Quite often they are corroded, specially with older boats
Hi Kors,
Good idea, I should have mentioned that.
I have a naive question: what does aluminium corrosion in the bilge look like? I have Googled but still don’t know. How does one distinguish it from harmlessl scurf one might find in a bilge?
Hi Ron,
If it’s true corrosion there will be white powder or paste if it’s wet. Wipe that away and then look carefully with a magnifying glass for pitting.
Agreed with John and all the comments.
One detail, use Tef-Gel (made by USS) on all SS screws on the boat. “Ted-gel” os mentioned. Perhaps a typo, but beware of the several knock-offs with names very similar to TefGel.
Emphasize looking inside the water tanks. If they are unpainted, and have never had chlorinated city water in them, probably OK. They may have hundreds of white pustules a few mm diameter.
If there is not a decent visual access to the tanks, I would insist on one being cut for survey, if that is at all possible.
Look carefully at any beautiful recent paint. Some years ago I was in Garcia’s yard and saw them cutting off and replacing most of the bottom plates. The boat had sailed from Australia to Europe with a wind generator using the hull as the negative “wire”, been seriously pitted, then filled and painted for selling. Not surprisingly, Garcia’s customer and the previous owner were in court.
Above based on 20 years sailing an aluminium boat, with (so far) no corrosion issues, following John’s advice, and meeting a goodly number of other owners. Don’t let the age alone of the boat put you off.
Kors and Neil,
thank you for your suggestion about checking inside the water tanks.
It looks from the pictures that the access is good so I should be able to look inside through the inspection hole.
As well as the shaft tunnel, I’d suggest also looking closely anywhere steel, stainless, or any other metal, is in contact or even within cooee of the aluminium. I’ve inspected many offshore structures where the Al has completely disappeared from galvanic (dissimilar metal) corrosion. Check behind base plates even if they have rubber insulators, remove some bolts and check bolt holes for enlargement. In my experience you don’t need contact for dissimilar metal corrosion – if the components are close enough, and wet and salty enough, the electrons find a way.
Hi Dan,
Absolutely, but that’s more deck stuff that can be fixed relatively easily, and Michael was interested in deal-breaker issues with the hull.
Hi Guys,
I’m doing inspection on that 24 years old Aluminium yacht now.
Today I’ve found some underwater corrosion under the paint.
At this picture you can see the worst area:
https://drive.google.com/file/d/1nBz1ZDXBK1w3LkEcYvZfHVkCI4ojTven/view?usp=sharing
I’m aware that on such a old boat there will be some corrosion. However, I’m wondering could this level of corrosion is something to go away?
Electrical check tomorrow.
Thank you for any advice.
Michal
Hi Michal,
Yes, that does not look good. Definitely an electrical check both in and out of the water is required, plus removal of all the paint etc covering the damage so it can be properly assessed. I would also look for dissimilar metals under the water. That lower rudder bearing carrier looks suspicious to me. Also, the rudder may not be properly connected to the rest of the hull.
Hi John,
thank you for reply. We just went back from inspection. Electrical check with silver chloride reference cell showed problem with stray current (decrease of potential from -1,026V to -0,886V when connecting shore power). Then we took the boat from the water and have found corrosion (pitting) around the hull. Also deep galvanic corrosion around two thru hulls.
But I’m still not 100% sure if this is enough to give up this boat (I can probably get very good price and I like other aspects). The aluminium in the bilges looks like new (except around those 2 thru hulls).
I think I need a consultation with good marine surveyor that knows aluminium problems. Can you recommend anyone?
Hi Michal,
Sounds like you have found the problem.
The only person I know is Tony Knowles, who surveyed my boat when I bought her, but I’m not sure if he is still in business: https://www.yachtinsidersguide.com/listing/newport-marine-surveyors
Hi Michal,
Steve D’Antonio is an occasional contributor to AAC on technical matters and an ABYC Certified Corrosion technician, and consultant. More about his work can be found at steve d’antonio marine consulting (https://search.yahoo.com/search?fr2=p%3ads%2cv%3aomn%2cm%3asa%2cbrws%3achrome%2cpos%3a1&fr=mcafee&type=E210US714G0&p=steve+d%27antonio+marine+consulting) where numerous articles on corrosion may be found.
He has read your initial question and, although quite busy right now, may be helpful remotely.
Good luck with this.
My best, Dick Stevenson, s/v Alchemy
Hi Dick,
thanks a lot! I saw his wise comments but I didn’t know that he also provides consultations
I wrote to Steve.
All the best.
Michal
Hi Michal,
I don’t know if you’re still looking, but perhaps this may come in useful for other prospective buyers as well.
My partner and I have been searching for an aluminium boat to buy for the last 6+ months (set on that the path by reading AAC!) and, like you, went through the process of asking: “how bad does the corrosion have to get before it’s a deal-breaker?…”
We’ve been working with Colin as a consultant, so he has patiently instructed us through that process, which has been great learning.
Because we have considered options in both Europe and the Americas, I posted on alloy boat groups for surveyor recommendations and then reached out to ten (ok, maybe it was a few more than that…) or so surveyors and went through the process of reading sample surveys. I can recommend the ones below based on interactions with them and sample surveys only, since we haven’t gotten to the stage of surveying yet!
(All of these surveyors are open to traveling.)
If you’re based in the U.S., I received many recommendations for Dylan Bailey (he will do ultrasound as well). He has been very responsive and helpful by email but could not currently travel beyond the U.S. and Caribbean. Jon Howe, in Florida, is semi-retired, but he may be open to surveying within the state (otherwise he will recommend Dylan!).
If you work with a surveyor who can’t do ultrasound, but would like ultrasound testing, Certified NDT in Washington do ultrasounds only (no surveys). They are very available by phone and email.
In Europe you might consider Davide Zerbinati (Italy), who is extremely responsive and very detail-oriented. He also supervises builds and repairs.
In France, Loic Blanken has a very good reputation and is also prompt and available.
The same is true of CEEMIN (which was founded by Yvon Quernec).
Lamarque & Guyon also have a good reputation, but I have not been in touch with them.
Theo Van Rijwijk, in the Netherlands, was very helpful via phone, very willing to travel, and is a metallurgist. His sample survey was very detailed.
I have to say that, so far, the surveyors I’ve reached out to have been the most forthcoming people in the marine industry, willing to share information on what to watch out for even when they weren’t available to survey and so didn’t stand to profit from it. I was deeply appreciative.
Anyway, if you’d like any further info, I’m happy to share. And, good luck with your boat search!
Cheers,
Alessandra
Hi Alessandre.
Great information, thank you!
Hi Alessandra,
thank you for your awesome comment!
You saved me (and probably others) plenty of time.
I gave up the last boat that I visited, but I’m still looking. Next week I’m going for a trip to Germany and Netherlands.I’m in Poland right now. If I’ll find promising boat I’ll probably make a contact to mr Theo Van Rijwijk from the Netherlands.
Thanks again and good luck with your research.
Michal
Hello John and Phyllis, I’m a long-time subscriber who is under contract to purchase a late model aluminum hull Allures that is located in Martinique.
I spent the morning reading your material about aluminum hulled vessels. Thank you for all of that great information. (It is a bit intimidating.)
The survey is scheduled for next week in Martinique. The problem is that my surveyor cancelled due to a health emergency.
I’m seeking another surveyor who has experience with aluminum hulled vessels, and wonder if you or your e
Readers have any recommendations?
Hi Thomas,
I don’t have any recommendations given that both guys I used are retired, but have a read through the comments above, there are several suggestions there. Particularly Alessandra’s comment.
Thank you John – I missed those recommendations in my reading. I’ll pay more attention to the comments in the future!
Hi John,
I’m planning for a preliminary inspection of a 50 year old aluminum boat.
She’s currently on the hard, so the surveyor will be able to start with a full visual inspection of the hull and encapsulated lead keel.
I’ve already received some concerning photos from the broker that show a big difference in the condition of the hull fairing layer above and below the waterline.
Topsides look great.
Below the WL, however, both hull and rudder have some areas of distinct texture. Also, it appears that sounding with a hammer during an insurance survey last Fall revealed some areas of loose fairing compound and/or paint. (All of this gleaned only from photos.)
The owner says the boat does not have an issue with corrosion from electrolysis and he has been wary of making any changes to the electrical system it came with when he took ownership ~10 years ago. (As of yet it’s unclear to me whether the electrics include an isolation transformer, but the boat has benefited from numerous upgrades to other major systems, all under owners prior to the present one.)
My questions:
-Could this loose fairing compound be a sign of corrosion? Or is there a natural lifecycle to the adhesion of a fairing layer?
-After visual inspection inside and out, would the most efficient next step be to inspect the shaft tunnel? Seems like that could get to the heart of the matter quickly, if not inexpensively.
I’ll try to upload photos that show some of the concerning areas.
Thanks in advance for any advice!
Scott
https://i.imgur.com/0q2vGTX.jpeg
https://i.imgur.com/BoQFVV5.jpeg
Hi Scott,
The loose fairing could be either but my guess would be failure of the bond. That said, to be safe any loose areas of bonding should be removed to see what’s going on. And anyway, if the bond is failing a complete bottom job is on the cards and should be in your budget.
And yes, a shaft tunnel inspection is a very good idea, although so doing does not guarantee you that there are not problems some place else.
As to the assurances of the owner, I would suggest ignoring them and instead going through this check list: https://www.morganscloud.com/category/aluminum-boats/care-tips/
Very few people, including owners of aluminium boats, actually understand stray current and dissimilar metal corrosion, so this kind of assurance is pretty useless. To check ask him if he can give you a record of the regular tests he did with a silver chloride reference cell. If you get a blank stare the question of competence is answered.
I would also suggest doing your own detailed inspection since most surveyors, with a few exceptions, have no idea how to properly check over an aluminium boat…or any boat for that matter.
Hi John,
Many thanks for your advice. That’s all helpful guidance as I try to determine the scope of work needed to remedy some obviously deferred maintenance on this classic boat.
By a full bottom job, I assume you mean refairing. In your experience, is it generally possible to get a good secondary bond on the remaining solid areas, or should I consider this an “all or nothing” type of repair? (As a younger man I did antifouling and blister repairs on several fiberglass boats, but never aluminum.)
I’ll continue to study AAC’s aluminum hull care articles as I prepare to “survey the surveyor”.
I may have found a good one: Besides being a senior-experienced surveyor and instructor, he’s an ABYC certified electrician who offers a specific service for in-water detection of stray current. I will ask about his experience with metal hulls. With the knowledge I’ve gained from these pages I feel well prepared for my interview with him later today.
Kind regards,
Scott
Hi Scott,
Generally if the bond between the aluminium and the first layer of the paint system has failed in more than about 10% of the area, it’s time to start again.
What sort of boat? The underbody looks M&R. And where was she built?
Hi John,
Thanks for the detail on how to gauge the extent of the bottom maintenance. I know that the hull has been reconditioned at least once since she was built (by Luke in Maine), but I won’t be surprised if it’s time to redo the bottom.
I’ve gone ahead and contracted the surveyor I mentioned to make a preliminary exterior inspection. He and I reviewed the most recent insurance survey and photos and I was satisfied that he has the required expertise for this part of the process.
Best,
Scott
Hi John and all,
Following on your surveyor comment…
On surveyors:
Firstly: What is the survey for? In order of their need to have competence: New boat survey (both when building and when “finished”), repair (especially if interfacing with the ins. co.), pre-purchase, and, lastly, the periodic surveys for insurance. For new boat and repairs and pre-purchase (especially if purchasing sight unseen), it probably pays to really check out the competence of the surveyor and not just take the local boatyard’s suggestion.
I think the best background (perhaps crucial) for a marine surveyor is to have years of experience in boat repair and, less importantly, lots of general boat yard work. This is sometimes hard to determine. I would go with the direct approach and ask: “What have been the most important contributions to your becoming a good surveyor?” and see where that leads. Without the above, a surveyor can still be competent, but he/she will have to really work hard to catch up and accumulate knowledge: this seems to me best accumulated with hands-on knowledge. What little I know of the training/credentialling of surveyors sounds pretty lame, so they are on their own.
My cruising life has led me to have the occasional insurance survey in different locations where I had to rely, sometimes not in English, on local suggestions (3 done in the US or UK). Even with a bit of due diligence, I have been uniformly disappointed (one even wrote the book on surveying). I could go through a list of things missed, things mis-represented, outright errors, etc., but the insurance co. was always satisfied and that was the more important outcome.
I was always interested in learning from tagging along with the surveyor, but rarely did learn anything new. For those owners interested in the survey helping them have a more seamanlike vessel and to learn about their boat, I suspect they will be disappointed. I also suspect that insurance surveys do not bring out the best in surveyors (see below): these surveyors may be more conscientious and interested in pre-purchase and repair surveys.
The surveyors which were important to Alchemy and with previous boats were ones I knew personally and they really contributed to my boat’s being seaworthy and to my own knowledge.
A good survey can be very helpful.
There are many things that go on in the marine world that I consider drive boaters to spend their money on a cottage in the Berkshires and away from boating. Boat yards that communicate poorly, go way over estimate for repairs and take far longer than promised are high on that list( and push the owner far from irritation and more towards rage. There is no excuse. Far less high at provoking irritation, but still irritating, is the self-serving folie à deux that I see taking place between insurance companies and surveyors. The insurance companies feel like they are insuring vessels deemed safe (likely illusory) by surveyors who are paid a lot and who are likely only to discover the more egregious examples contributing to an unsafe boat: examples that very likely should be known by the owner.
I am sure there are examples, but in all my years boating, I have yet to hear of a skipper saying how pleased he was with a survey as there were unsafe conditions found in the survey. More often it is more along the lines of, “Yes, I have to up-date my flares: he had to find something to report…”
To me this smacks of: “You scratch my back and I’ll scratch yours.” My (the surveyor’s) bread and butter derives from you, the ins co, insisting on regular surveys and you, the ins co, will have CYA.
Again, I am sure there are examples, but I have yet to hear of an insurance co holding a surveyor responsible when a boat surveyed gets in trouble. Nor have I heard of a surveyor being held accountable for something missed. Just reading the caveats at the end of the survey indicates all the ways of slipping away from accountability. And it takes little effort to find reports of ins co’s attempting to slip away from responsibility.
Enough of this harangue.
My best, Dick Stevenson, s/v Alchemy
I would like to see us, as recreational boat owners, find some way of rising-up and protesting certain practices that really diminish the enjoyment that one can derive from our sport. This goes particularly for those just getting into the sport and those who choose to rely on what they hope will be reasonably priced and timely accomplished good service for their vessels.
Hi Dick,
As someone who has only sailed and repaired others’ boats, I have comparatively little experience working with surveyors and reading surveys.
However, it doesn’t take much of a sample size to find evidence of carelessness. I recently read a pre-purchase survey that recommended “matching gelcoat repair by a qualified FRP technician”— for scratches on an aluminum hull 🙂
Best,
Scott