How bad is pitting along the waterline?

[AlX]

I'm interested in buying a 10/6/4 narrowboat from 1993. Base plate and sides are in quite good condition (thinnest points 9.5 and 5.7mm respectively) but there is pitting to 1.75mm along the waterline (1mm on base plate). How much of a problem is this and how much does it reduce the value of the boat?

[Alan de Enfield]

4 minutes ago, AlX said:

I'm interested in buying a 10/6/4 narrowboat from 1993. Base plate and sides are in quite good condition (thinnest points 9.5 and 5.7mm respectively) but there is pitting to 1.75mm along the waterline (1mm on base plate). How much of a problem is this and how much does it reduce the value of the boat?

 

Do you mean there is pitting to 1.75mm thickness or, there is pitting 1.75mm deep in a 6mm side ?

 

If it is the former, then you need to do fairly urgent work and get it overplated as it is not insurable** as is.

If the latter, then it is pretty serious in as much as soon as you get pits as deep as 2mm the sides become rated as 4mm thickness and it becomes uninsurable**.

 

** Fully comprehensive,

You can still insure it 3rd party which is enough to get your licence, but obviously if it sinks then you 'lose' everything.

 

 

Is this to be your first boat ?

If so, buy the best you can, you will have enough to learn and worry about with having the hassle of worrying about insurance, will it sink etc etc.

Try and find as 'young' a boat as you can - no guarantee,s but it is likely you will have less ongoing problems with a 15 year old boat than you will with a 30 year old boat.

[MtB]

1 hour ago, AlX said:

I'm interested in buying a 10/6/4 narrowboat from 1993. Base plate and sides are in quite good condition (thinnest points 9.5 and 5.7mm respectively) but there is pitting to 1.75mm along the waterline (1mm on base plate). How much of a problem is this and how much does it reduce the value of the boat?

 

 

Bloody hell, how fast is the water pouring in through the remaining 4.25mm thickness of steel?

 

 

 

 

[Guest]

2 minutes ago, MtB said:

 

 

Bloody hell, how fast is the water pouring in through the remaining 4.25mm thickness of steel?

 

 

 

 

 

I suspect what the 'old boiler fixer' is trying to say is 1.75 mm from 6 mm is not something to be overly concerned about.

 

Unfortunately rather than just say that he often prefers to talk in riddles. Something he seems to reserve for new members who may not fully grasp his penchant for doing this.

[Stroudwater1]

It sounds like there’s some significant pitting. It depends what the surveyor suggests next and what’s happening with the boat.  It also depends on whether it’s on brokerage as negotiations could be easier. A private seller could bodge after turn down your offer then sell”sorted” to an unexpecting other person. Or get it done properly and ask a lot more possibly. 
 

some surveyors may suggest grit blasting to assess further, including the baseplate and if nothing is deeper then pit weld the deeper pits if as sounds likely is necessary  (fill in the deeper pits with welding ) and then epoxy the hull. That will probably cost £8-10k but will give a boat likely to last for a good many years. That ought to be at the current owners expense. If on brokerage then it depends but a decent broker would take your deposit agree the works needed ideally agree if worse is found return deposit and move on) then sell with the surveyor happy with work done and you have a decent though not 100% perfect hull that will last for many years. 

If  the survey has been done and no more is said then then really you need to factor/negotiate  at least £10k off the boat though that’s possibly a risk as worse pits could be found needing overplating that affects future value. It’s also a sellers market with boats selling fast. 

you could chance it black it every two years at much less cost each time and it may last a number of years but epoxy etc will give you longer  

 

As MtB acerbically states after a bad day (🤣)  it’s not a disaster but as  Alan de E states it’s heading to need significant remedial work and the sooner the work is done the better say ideally this year. 
 

It’s a way of getting a slightly cheaper boat with a good chance of a long life if done properly. Alan is right buy a younger boat and less to worry about but ideally do epoxy as you will probably end up in the situation yours is in after a few years unless you really do black the boat every two years plus the base.  

 

there is a wait to get a boat epoxy and pit welded too. 
 

I suspect others may disagree with me. 
 

 

[MtB]

3 hours ago, Stroudwater1 said:

I suspect others may disagree with me.

 

E.g. me!

 

The opposite point of view is this boat is already 29 years old so approaching the end of its designed life on any number of fronts, hull corrosion being only one of many factors. At 29 years the interior is probably desperately dated if not also worn out, the shell is probably insulated with rockwool rather than spray foam,and the exterior paintwork well on the way to needing doing again.

 

At the current rate of corrosion, 1.75mm of pitting after 29 years of use suggests this hull will have corroded right through in another 71 years. I'd buy this boat and just get on with using it were it me, with no particular special treatment other than regular blacking, switch to TPI if/when it gets down to 4mm hull thickness and wring another 29 years of life out of it before any serious hull work is really needed to stop it sinking. In fact the boat would probably outlast me. 

 

What would have been the intended life of a new narrow boat, back in 1993 when this one was built?

 

And what do builders say the intended life is of boats they build now? 30 years would be my guess...

 

I suppose my point is, if one is buying an old boat towards the end of its life, one might as well just get on with using it and accept that it is degrading with age, rather than try to stop the clock with tonnes of overplating when the boat is at no practical risk of sinking for another 30 years at least.

 

 

 

 

 

 

 

Edited March 8, 2022 by MtB

[Stroudwater1]

Is the rate of corrosion a constant MtB? I have a suspicion it’s not??  
 

It does depend whether the boat was a good one to start with or not, there’s some pretty decent 1990s boats whos builders wouldn’t imagine ever scrapping. It depends on the intended use and much else.  Some boats have been properly upgraded along the way. 
 

 

 

[David Mack]

8 minutes ago, Stroudwater1 said:

It does depend whether the boat was a good one to start with or not,

Well not really. Good and bad boatbuilders will all have used the same general purpose mild steel available at time the boat was built. How it has been looked after in the years since will make far more difference.

The only caveat to that is that a few boatbuilders used intermittent welds to attach guards (rubbing strips) and this can allow water in behind where corrosion occurs unchecked.

Edited March 8, 2022 by David Mack

[ditchcrawler]

That sort of damage could have happened in the last couple of years, remember @Keeping Up experiance

[Alan de Enfield]

30 minutes ago, ditchcrawler said:

That sort of damage could have happened in the last couple of years, remember @Keeping Up experiance

 

 

Was that the one that went from 6mm thickness to 2mm thickness in about 18 months ?

(Due to electrical wroms worms escaping from other boats and eating his hull ?)

[Keeping Up]

22 minutes ago, Alan de Enfield said:

 

 

Was that the one that went from 6mm thickness to 2mm thickness in about 18 months ?

(Due to electrical wroms worms escaping from other boats and eating his hull ?)

Yes it went from 6mm to 2mm in about 18 months (quote from the surveyor, "at this rate you'll soon be the proud owner of a 70ft submarine" but we never established the true cause. It may have been other boats electric worms, or an electrical supply fault (they did admit to putting 30v down the earth line for a while), or stray electrical currents possibly through the exhaust system to the engine block, or something non-electrical such as pollution in the water, or something else entirely. We will never know - we re-wired the boat, put an isolating transformer in the supply, etc etc, and had no more problems after the re-plating.

[MtB]

5 hours ago, Alan de Enfield said:

Was that the one that went from 6mm thickness to 2mm thickness in about 18 months ?

 

In which case why would overplating stop it? 

 

Surely overplating with 5mm steel would only add a year for life at that rate! 

[beerbeerbeerbeerbeer]

7 minutes ago, MtB said:

 

In which case why would overplating stop it? 

 

Surely overplating with 5mm steel would only add a year for life at that rate! 

I don’t suppose it would have stopped it if he hadn’t addressed the issues which he posted ^^^

[Alan de Enfield]

10 minutes ago, MtB said:

In which case why would overplating stop it? 

 

 

 

It won't, but it was not suggested that it would.

 

Every time this sort of thread starts you respond with "its lost 1mm in 20 years therefore you don't need worry for another 100 years"

 

Your thinking is seriously flawed  - in principle if there are no changes to the environment they it may  'last another 100 years' but in reality our environment is variable - it just take the boat to have an electrical problem, or to moor close to a boat with electrical worm leakage, or for the rich nitrogen waters in Rural canals to develop MIC, etc etc, there is in fact a far higher chance of the speed of corrosion increasing than there is that it will stay the same.

 

KeepingUp is a prime example - gone from no corrosion for 'years' to serious corrosion and thinning of the plates from 6mm to 2mm in just 18 months.

 

It may not be a regularly reported event, but there are 1000s of boaters who do not use this forum, and surely even one event proves that your statement is not correct in all cases.

[syd]

I was told around 1mm per decade average, provided the boat was looked after. With the boats I've had over the years, it seems to bare that out, well more or less.

But there are larger numbers on the canals these days, all wanting 240v via whatever means & mobiles, so I suppose rare things can and do occur.

 

OP regarding the pitting, if it were me I wouldn't worry to much about it, but everyone looks upon problems differently.

[Mike Hurley]

I would have thought that pretty much most boats at 30 years of age would have pitting, depends how the maintenance has been over the years. I saw a boat on the duck a few weeks back, 2006 and overplated, others from 1985 showing 1mm loss.

[AlX]

Thanks so much for your (quite divergent) views!! The pitting (at least where it is deepest, up to 1.75mm, and can become an insurance problem) seems to be only along the waterline. I guess over-plating this or treat otherwise isn't that expensive? Also the seller says they would pay for it but I wonder if the problem is then solved or just postponed. Interestingly, the survey from around 3 years ago which detected the pitting problems around the waterline didn't propose to take any measures.

[MtB]

17 minutes ago, AlX said:

Thanks so much for your (quite divergent) views!! The pitting (at least where it is deepest, up to 1.75mm, and can become an insurance problem) seems to be only along the waterline. I guess over-plating this or treat otherwise isn't that expensive? Also the seller says they would pay for it but I wonder if the problem is then solved or just postponed. Interestingly, the survey from around 3 years ago which detected the pitting problems around the waterline didn't propose to take any measures.

 

The thing is, steel boats go rusty and get pitted if you make them wet. How bad it gets before you feel the need to do something about it is more to do with your attitude and your insurance company's attitude to this fact than to do with the boat. The boat won't sink until the pits get to the same depth as the steel thickness. Ands even then it won't if your bilge pumps are good enough to keep up. 

[Slow and Steady]

16 minutes ago, AlX said:

Thanks so much for your (quite divergent) views!! The pitting (at least where it is deepest, up to 1.75mm, and can become an insurance problem) seems to be only along the waterline. I guess over-plating this or treat otherwise isn't that expensive? Also the seller says they would pay for it but I wonder if the problem is then solved or just postponed. Interestingly, the survey from around 3 years ago which detected the pitting problems around the waterline didn't propose to take any measures.

So the pits are 1.75mm deep rather than the steel being thinned to 1.75mm. Mine is similar - it's pure lack of maintenance IMO. Mine was shot blasted and 2 pac painted for this by the previous owner a few years before I bought it when the boat was less than 10 years old - I suspect the original owner just sat about in it and did zero maintenance as it only had a few hundred hours on the engine. The next owner did the same but at least they did blast and paint thing. That was about 6 years ago and it's still just fine. I've seen the pics and it's plain only the waterline was effected. Over-plating it is an over-reaction IMO but the shot blast and 2 pac seems like a good solution as it stopped the rust completely.

[enigmatic]

36 minutes ago, AlX said:

Thanks so much for your (quite divergent) views!! The pitting (at least where it is deepest, up to 1.75mm, and can become an insurance problem) seems to be only along the waterline. I guess over-plating this or treat otherwise isn't that expensive? Also the seller says they would pay for it but I wonder if the problem is then solved or just postponed. Interestingly, the survey from around 3 years ago which detected the pitting problems around the waterline didn't propose to take any measures.

 

Perhaps the most important thing is how much pitting is there and what's causing it?   You'd expect some pitting on a boat that age to 1mm or more. 1.75mm is a fairly deep pit, but if most of the rest of that pitting isn't that deep and the few really deep pits have been there for a while and possibly been treated in some way (filled with epoxy etc) so they're not getting any deeper you haven't got too much to worry from the insurers if you get your boat blacked on a sensible schedule. On the other hand if you've got microbes nibbling your way though the steel like the fortunately rare example Alan suggested it's more of a cause for alarm  (but fortunately that's a bit rarer than the corrosion from plain old water coming into contact with steel where there's a small gap in the blacking)

 

Only your surveyor who's actually seen it can really advise on that and whether he thinks it's heavily pitted all over or a perfectly normal 30 year old boat,.

Edited March 10, 2022 by enigmatic

[Stroudwater1]

The seller is paying so as I suggested earlier get the deepest ones pit welded then epoxied (on the base too) and all will be sorted for some years as long as you inspect and clean and retouch every three years. 
 

It won’t need overplating if this is done, I’m pretty sure. 
 

Yes boats rust but epoxy prevents much of this. 
 

Im not understanding some who seem to want all older boats to rust away, many have more charm than many modern caravan boats , many have better designed hulls than these days when most are dumbed down to an accountants bottom line rather than a boat builders sensibly designed bottom. 

It does depend on the boat of course, but many are worth persevering! 

 

[Slim]

My boat suffered significant pitting in it's first 3 years of life. I would say about 50 - 75 in number and up to about 1.5 mm deep. It didn't have 230 v installed as I was fitting it out as a hobby. I was moored alongside a well fitted liveaboard. After the first panic (extreme) I sat on my stool and spot welded all of the pits using a combination of my MIG and stick welders ( both hobby type kit). The following year I had it out of the water, checked carefully and found a few pits I had missed. Repeated process including out of the water the following year by which time the problem was resolved. Over the subsequent 20 years I've never left it more than 2 years between slipping and blacking and the consensus view is that the hull is, at 26 years of age as sound as any.

Should add that at the time  epoxying narrowboats was unheard-of 

Edited March 17, 2022 by Slim