new steel diesel tanks for a mobo, stainless steel or mild steel?

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I can't prove this but suspect lack of use or little use and lack of fuel turnover leads to water standing at the base of the tank and that promotes corrosion.
Lack of use seems to be the cause of most faults with boats .
 
madabouttheboat said:
Just a thought. But if you had new mild steel tanks made, would it be a good idea to line them with that liquid rubber stuff sold to repair leaking tanks before install?
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I replaced our 40 year old mild steel fuel tank when it rusted through with a slightly smaller plastic one. Mild steel fuel tanks do not rust through from the inside. The inside of the tank looked pristine when it failed due to outside corrosion.
The tank had lasted 40 years in spite of less than stellar maintenance by previous owners. I know the innards were perfect because I added an inspection hatch to it some years previously and removed two buckets worth of crud from the bottom.
 
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Outboard fuel tanks and plastic motorbike tanks.
It's not something that is noticeable until the tank is in a locker or you put decals on a tank.
 
Rappey said:
Outboard fuel tanks and plastic motorbike tanks.
It's not something that is noticeable until the tank is in a locker or you put decals on a tank.
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I suspect that the decals not holding has more to do with spillage during fueling than with any permeance of the material. We store petrol in plastic canisters for all sorts of reasons at home and in enclosed spaces and I have never noticed any transmission.
 
Cynically, I would say it rather depends on how long you intend to keep and use the boat.

When you come to sell it, I doubt the type or cost of the tanks will make any difference to the price.

If you intend to keep her for some while then longevity is more important. I think pretty much all the materials you mention will last 10 years.

After that there is such wide debate and everything that has been tried seems to have a potential draw back.

Steel will probably last for the least long, the rest maybe not much to choose, but I suspect it also comes down to a lot of other things, like how good the welds are, whether the metal (or plastic) is up to spec., etc.

I sometimes wonder whether several small tanks is the way to go with connections between. At least this way it is far easier to replace the tanks as needs must.
 
Laminar Flow said:
I suspect that the decals not holding has more to do with spillage during fueling
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Not all all. One tends to not spill fuel over a hot motorbike engine when refuelling on a garage forecourt..
Tank decals for plastic tanks are sold perforated and some sites give an explantion as to why and the option for non perforated for steel tanks. If they are not perforated to allow evapouration/permeance the decals shrivel and come unstuck !
Outboard fuel tanks in a confined storage compartment on a boat, the locker goes black and a jelly like substance builds up if left unchecked.. Again its fuel permeating through the plastic.
 
Rappey said:
Not all all. One tends to not spill fuel over a hot motorbike engine when refuelling on a garage forecourt..
Tank decals for plastic tanks are sold perforated and some sites give an explantion as to why and the option for non perforated for steel tanks. If they are not perforated to allow evapouration/permeance the decals shrivel and come unstuck !
Outboard fuel tanks in a confined storage compartment on a boat, the locker goes black and a jelly like substance builds up if left unchecked.. Again its fuel permeating through the plastic.
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Learn something new every day - will be moving our generator fuel to a more ventilated place.
 
I didnt believe it when i was first told.. I have a 16ft centre consol.. The 30 and 20 litre outboard tanks are under the seat.. It does have vents but the boat has a full cover and if i dont use it much the tanks turn black with hardly any red visible.. Its horrible stuff as you also get covered in it just touching it.. Easy to clean off the tanks but a pain.. I might try spraying the inside of the storage area with patio magic and see if that does anything.. It appears to happen in confined spaces . Left in my shed there is no problem.
 
Rappey said:
I didnt believe it when i was first told.. I have a 16ft centre consol.. The 30 and 20 litre outboard tanks are under the seat.. It does have vents but the boat has a full cover and if i dont use it much the tanks turn black with hardly any red visible.. Its horrible stuff as you also get covered in it just touching it.. Easy to clean off the tanks but a pain.. I might try spraying the inside of the storage area with patio magic and see if that does anything.. It appears to happen in confined spaces . Left in my shed there is no problem.
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We have had our new diesel tank for three + years now and it is still new, shiny and translucent. Perhaps diesel is less likely to permeate.
 
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