I am continuing to post on this subject as I continue to learn stuff that may help other owners. I had taken the aluminum fuel tank which was sweating only very slightly now and then, to the radiator shop, thinking they could clean it, test it, and re-weld any weak spots. The radiator shop said they tested it and found weakness in the bottom near the front end of the tank, an area about 8 inches by 6 inches, quite significant.
I couldn't see that, but took their word for it. I decided to take the tank to another metal fabricator, who said that diesel fuel is a lubricant and doesn't easily corrode aluminum. When it does, it should show as white powdery stain, none of which was visible on my tank. He thought my tank was still good, and might just need the lowest weld re-done, as he thought he saw a slight separation/crack in the weld. He sent me away to sand the outside of the tank with 80 grit paper/orbital sander so we could inspect it better, clean the inside with Castrol Super Clean and rinse with lots of hot water to get rid of all diesel in preparation for any welding, and bring it back to him for repair.
As the tank is 36 years old, and others have posted about leaks in their tanks, I decided to also get quotes on a new tank. I received three quotes, $690, 700 - 800 and 1,400 in Canadian dollars, all for the same tank based on the picture and measurements I sent them. Time frame quoted was one week, three weeks, four to six weeks and two months. I actually asked for more quotes, but three other metal fabrication shops didn't get back to me.
One fabricator, who sounded very knowledgeable, said that the diesel fuel does affect the aluminum so that despite attempts to clean it, it is still hard to get a good weld repair or epoxy adhesion, and therefore he would consider any such repair as a temporary fix, not a longer term permanent repair.
As the weld repair would likely cost $200 or more, I decided to go with the $690/one week quote as I don't ever want to have to remove the water heater, locker floor, fuel tank and all the associated fluids, lines, etc. again, and want the peace of mind that it's a good fix.
My experience shows that one should shop around as estimates can vary dramatically, and opinions and knowledge about products and repairs varies significantly. Unfortunately, it makes it hard to come to a sound, fact-based decision for those of us who are mainly sailors, not engineers or other specialists. I generally try to do most work on our boat myself when possible, taking lots of time, care and attention, hire reputable specialists when I'm over my head on a project, but think it through carefully, getting as many different quotes and opinions as reasonable.
Next week l'll install the tank, locker floor, new water heater to replace the 16 year old current one. It will likely take me two days to do that, making the various connections, electrical and plumbing as well as heat exchanger, adding coolant, bleeding the fuel system, etc. I will likely have saved about $1,000 or more doing that work myself rather than hiring a pro at $100/hr.
And then I can go sailing again!
Frank
