Fuel Tanks in Ocean's

Diesel fuel is generally a pretty lousy conductor. That is why it is subject to risks from static charges generated when fueling at high rates.

I really doubt that the SS pickup tube is responsible for the pitting you see. Is the area under the pickup lower than the tank bottom? Is there a sump there? Did the tank ever sit with a large amount of water in it? How far from the tank bottom is the pickup?

It is possible that movement of fuel to the pickup leads to water collecting in that area and causing the pitting.

How bad is the pitting and pin holing around the tank penetration for the pickup?

You can't have electrolysis without an electrolyte.

Getting 20+ years out of an Aluminum tank that sits a few inches above bilge water is very good. I'd highly consider replacing the saddle tanks at the same time.

I'm sure glad neither of my 3 fuel tanks or water tank leaks after 29 years. That job looks … horrific.

Yep. Notice how clean and pit free it is in the immediate area around the pickup? That's because the higher relative velocity of fuel (because the pickup is so darn close to the bottom) in that area did not allow water to sit on the bottom and create corrosion cells. The general shape, size, and location of the corrosion shows where water migrated toward the pickup and collected. That water fed the bacteria that produced the waste products that ate the aluminum.

Yards don't think, the people you talk to in a yard think but not always clearly.

To me it looks like a tiny bit of saltwater is getting in through the vents or the fills the way the metal is pitted. That is where it is going to end up from all of the tanks and the other tanks shouldn't have water issues. The 63' Ocean has a large saddle tank on the outbound side of each engine, and both of those tanks have a hose at the bottom that gravity feed into this tank which is in the ER aisle underneath the floor. The top of the tank in question, is below the height of the bottom of the saddles that feed it and everything draws fuel off of this tank.

Hi,

Ferrous material from drilling and cutting that is not removed can also cause pitting when in contact with the tiniest bit of water.

Excellent point. Aluminum boat owners should be very careful about wire clippings and drill swarf in the bilges.

It does not take very much water to cause that damage over a great number of years......Basically 3 tablespoonfuls is all that would take over years of time, the pickup would never pick that up since it is much higher. Since fuel floats, the water always stays at the bottom, there is also not a big surge or movement of fuel in that tank because the saddles keep it 100% full all of the time, unless you're below the last 300 gallons of capacity on the entire boat.

And also the comments about pieces from drilling the tank is a valid point. On the 63' Ocean I managed, Ocean drilled the 1/2" hole for the pickup and dropped the bung in the tank. It floated around in that tank for 19 years until it got caught in the very same pickup it was drilled for. We had awesome water pressure for 2 seconds, then it would just barely trickle (it was sucking through the pilot hole), then we inspected the pump and the intake hose was totally collapsed, we tried to blow the pickup out and couldn't and pulled it out and found the piece stuck in it, 19 years later.

I'm unclear under what circumstances the insurance would cover this. I love the concept of buying into coverage that would mitigate major repairs on a used boat. I'd love any help in understanding this.

BJG, going through the exact same challenge on our 63' as we speak. Would love any insite before the saws-all's start ripping in. Not exactly an easy location to excavate a tank out of.
cheers

Have any of you guys with these problems looked at fuel tank liners?