1987 CD36 Fuel Tank Replacement - Test Post

[Doug Gibson]

My major winter project is underway to replace my fuel tank. I've had small amounts of fuel seeping into the bilge for the past season. So, I took a deep breath and cut a big hole in the main cabin floor, not sure what I would find. The tank sits in a nicely molded fiberglass pan, which in turn sit on top of the keel ballast / bilge. I found about 2-3 gallons of water/diesel/sludge in the pan. The tank has several major poultice corrosion sites on the bottom and side of the tank where it was submerged in the muck. I could easily poke a screwdriver through these site, so the source of the seepage is clear. I will be ordering a replacement tank this week.

I have 3 questions / decisions I'd like input on:

1) The fiberglass pan has no drainage holes. I assume this was done to keep any fuel tank leaks from finding its way into the bilge. Unfortunately, it also holds any water than gets in the pan, which ultimately contributed to the failure of the tank. Since I've owned the boat, I've had a couple cases where I had water high enough in the bilge to spill into the fuel tank pan. So, I'm tempted to drill some drainage holes in the pan to make sure that any water that winds up in there does not remain. The pan sits about an inch off the ballast in the keel, so water can drain to the bilge. Any thoughts or reason not to do this ?

2) When I rebuild the cabin floor, I'm trying to decide if I should include a removable panel/hatch of just reinstall a permanent floor with the same, small access hatch. Has anyone rebuilt their floor with a large access panel? If so, do you have any pictures/advice?

3) From pervious postings, I know I can get a quality tank for Florida Marine Tank or Luther's Welding. However, I'm in the SF Bay area and am having difficulty finding a local shop. Any recommendations for tank shops on the west coast?

<img src="http://www5.snapfish.com/snapfish/slide ... =snapfish/">

[Skylark]

Brave man...
I would put a fitting in lowest end of the pan. You could then use this to drain or pump out anything than accumulates. Also, the same for the new tank. From the inside any condensate is cause of corrosion. Being able to remove the condensate would help a lot. However, it looks like the sides and bottom of your tank were not painted with the green zinc chromate paint and the corrosion occurred from the outside. Is that true?

I would definitely keep the access. The lack of access is one of my pet peeves. It make everything difficult to repair and maintain. Since I live aboard I have become a contortionist.

Thanks for posting the pictures. I suspect this task will be on my list in the future. When (not if) I do the same, I will try to remove the entire panel first without making any cuts. On Skylark it looks like the bulkhead at the nav station in cut under slightly to allow the floor panel to be angled up and lifted out from the opposite (port) side.

[Skylark]

PS:
But then I wonder; can fiberglass make a good diesel fuel tank? Just bond a top on the pan. Probably not a great idea, the way the holding tank turned out. Most end up leaking.

[Skylark]

PPS: might be ok as long at there no ethanol in the fuel http://www.boatus.com/seaworthy/fueltest.asp

[Skylark]

Or perhaps you replace the tank with a fuel cell/bladder http://atlinc.com/marine.html.