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When we purchased Marquesa I noticed there was a hip tank under the quarterberth. It had one of the magnet drive gauges that read 3/4 full but there was nothing attached to the intake or return connections on the tank. I filed it away and turned my attention to the massive main tank in the engine room. That tank looks to be 100 gallons or more.

Fast forward to now.

My plan was to recover that tank and use it to feed the Webasto heater and the Frankenmaker on a day-tank basis. Well the first thing I discovered is that it's not 3/4 full. The gauge is simply stuck. When I probed the tank the probe came up with something like dry sand on it. I've never seen aluminum oxide like this so it's kind of a mystery. So I thought, Ok I'll put some fuel in it, swish it around and get the crap cleaned out and go from there. But I'm glad I didn't. Instead I pulled it and found a few holes rusted through it. Who ever installed it bedded it down on foam backed vinyl. What kind of idiot puts a sponge against a metal boat tank? I spent the day cursing and getting it out of the boat. Now I'm mulling over repair/replacement options.

Here are a couple pictures. BTW I spent the rest of the day clearing all that trash out of my cockpit.








George

"What kind of idiot.."???

The "idiots" at Tillotson-Pearson bedded the aluminum water tanks in my Freedom 40 Aft-Cockpit Cat Ketch (Hull #61 of 63) in expandable foam. The (elsewhere mentioned) long-standing deck leak (from the midships scupper on the port side) rotted the bulkhead and saturated the foam, corroding the port tank significantly from the outside-in. It has now been empty for several years, as it won't hold water. One day I'll cut the top out and figure out how to fix it...probably by cleaning it out very well and pouring in enough epoxy to cover the leaks. Meanwhile, I'm hauling around 100 gallons of air which is detrimental to boat trim.

I have a bladder tank but I wanted to use it in addition to rather than just instead of. I think I'm either going to a. Break down and purchase a tig that can weld aluminum (mine only does stainless and other ferric metals) b. take to someone and have them weld it c. epoxy repair the holes and sheath the entire thing in fiberglass cloth and west system d. make a new tank out of fiberglass and epoxy. I have to talk to some guys about welding up the frame for my top anyway so I'll probably drag the tank along with me. I'm typing on my x-mas present so I can't really ask Santa for a tig welder.

There is also an abandoned steel tank that's centerline under the cockpit sole and I think that it was a fuel tank at one time. There is also a plastic water tank down there that I have not been able to draw from for some reason... sigh. I really didn't want to rip up my sole but I may have to at some point.

George

I had my ally tank welded up recently (which solved my problem, fortunately), while it was away I was thinking that I would have to glass it to take care of some pinholing, so I sent off to West System for details of how to fix it (we had glass tanks in the family boat when I was a kid).
This should be something anyone with a little glassing experience can do.
Here is the reply from West System

Our WEST SYSTEM® "User Manual & Product Catalogue" can be downloaded from our website:
http://www.wessex-resins.com/West_Syste ... manual.htm

In the past testing has been carried out on the use of WEST SYSTEM® epoxy for fuel tanks. WEST SYSTEM® epoxy at this time showed good chemical resistance and could be used in fuel tanks. Tests have been conducted on corrosion and softening of the epoxy after soaking in fuels and solvents; the epoxy displays excellent resistance to diesel and petrol but exhibits some vulnerability to attack from aggressive solvents after long term exposure. In consequence, wood epoxy composite fuel tanks should be carefully monitored over the long term because of continuing sophistication of fuel chemistry and the increasing use of additives and blends.
Apply four coats of WEST SYSTEM® and incorporate two layers of 471 glass cloth to the interior of the fuel tank for resistance to diesel and petrol. When constructing the tank, all joints should be made with generous fillets, tank openings should be oversized and coated with the same number of coatings as the interior.

Unfortunately we are unable to guarantee the use of WEST SYSTEM® epoxy for fuel tank use due to the sophistication fuel chemistry.

It is not recommended to use WEST SYSTEM® epoxy for coating drinking water tanks, although WEST SYSTEM® epoxy can be used for grey and black water tanks as these do not hold water for human consumption.

Prior to application of any epoxy you must ensure that good surface preparation is carried out as per the free WEST SYSTEM® "User Manual and Product Catalogue", (Clean - free of any oil, grease or other contamination, dry - low moisture content, and abraded - if hand sanding use 80 grit paper or coarser, if power sanding then use 40 grit paper or coarser). Specialist preparation for a variety of different substrates including Aluminium can be found in our WEST SYSTEM® "User Manual and Product Catalogue".

Katorpus,

If you remove part of the top of your corroded tank, perhaps you can put a bladder tank into the old one? It will hold a bit less water, but at least you have something, and you don't have to ruin your interior.

Funny b.t.w., how many different configurations TPI used; my 1981 F44#4 has a 100 gallon aluminum fuel tank under the L-settee and galley and a 175 gallon plastic watertank under the V-berth (very bad for the trim) and a 25 gallon plastic watertank under the port salon settee. The huge bilge is completely empty, so some day i'm going to install a huge wast tank there.

Michel

I'd actually pondered doing just what you described with the bladder, but concluded that pouring in epoxy might be a better approach. Until yesterday, I was unaware that anybody considered that cured epoxy resin might be a bad thing to be in contact with drinking water (although, with a little jiggering, I could dedicate the 80 gallon starboard tank to drinking water and use the 100 gallon (now-leaking) tank for showers, dishwashing, or whatever). In reality, with the coastal cruising I do, nothing in the tanks gets swallowed anyway.

My concerns with the bladder revolve around the extremely-likely presence of baffles in the tank. Removing the baffles would require removing virtually all of the top of the tank, to be followed by a lot of "upside down in the tank" time with a grinder to remove any edges deleterious to the integrity of the bladder. At the end of the day, I'd then have removed the only thing that keeps the tank wall from bulging (due to the weight of the filled bladder), which might result in a bad-news situation with the adjacent furniture (and maybe the bulkheads adjacent to it).

This might be alleviated by installing a horizontal "shelf" above the bladder. A 55 gallon bladder will leave a lot of leftover "room" in a 100 gallon tank, me thinks...

I haven't (at this point) even removed the inspection plate and stuck my arm in to see if there are any baffles IN there.

There's hardly any (usable) bilge space IN the aft cockpit 40. Nothing big enough for any tankage to speak of. I did install my a/c pump and raw water strainer for the a/c down there, but there's not a lot of space otherwise in mine.