Notes on the new diesel fuel tank

I had the new tank manufactured in April, 2010, at American Tanks, La Mesa, California.
The tank is constructed out of 1/4 inch aluminum and is separated by both a sealed bulkhead and a baffle. This yields two independent tanks; one is 22 gallons and the other about 50 gallons. Both tanks have their own vents, fuel returns and pickup tubes. They both also have independent 1.5 inch fill outlets. Cost of the tank was $1150 USD.

Prudence MAY have had the standard steel fuel tank under the vee berth. When I purchased her in the fall of 2001, she had a 90 gallon mild steel tank sitting in the bilge. This was a single tank, very heavy, and the aft edge almost ALWAYS sat in bilge water.

In 2004, I hoisted the tank out of the bilge for both internal and external inspection. Fearing I couldn't actually get the tank easily out of the boat, I elected to inspect the tank sitting in the cabin. Close inspection revealed very little corrosion on the aft lower edge. I steam cleaned the tank, cut out 3 - 6 inch inspection holes (there were NONE originally) and spray painted the tank. I also cleaned out the plastic sight-tube located on the aft edge as well as installing a new 1/4 inch shutoff ball valve on the lower edge of the sight tube.

In the spring of 2010, I noticed what seemed like a LOT of corrosion on the aft lower edge of the tank. Not wanting to find diesel fuel in the bilge, I decided to once again remove the tank, this time taking it off the boat. The tank cleared the main hatch by mere millimeters, but it DID come out!

Upon close inspection and by cutting off the now-corroded bottom, I decided to have a new, lighter, aluminum tank manufactured. I also decided to reduce the original 90 gallon size by about 10 gallons, by moving the aft part of the tank forward. This keeps the tank completely out of any water in the bilge.

The previous owner also installed a plastic "dam" across the lowest part of the bilge, evidently to keep any fuel leak out of the lower part of the bilge. This arrangement necessitated two bilge pumps, and all the associated plumbing.

I removed the dam when I installed the new tank was. This greatly simplifies the plumbing and associated headaches with TWO bilge pumps.

A few years ago I also installed a Cruz Pro digital, programmable fuel gauge. Among other outstanding features, this gauge can be programmed for odd size tanks. In other words, fill up 4-5 gallons and TELL the gauge this is 5 gallons. Fill 'er up with another load and do the same. Since the tank is sloping at the bottom, and goes from 11.5 to 15 inches across, this is the ONLY way to get an accurate reading on the remaining fuel. The gauge can also monitor fuel flow and indicate gallons/hour. Nice! 

Along with the gauge I installed a WEMA stainless steel fuel tank sending unit. This device has a 1/2 inch rod from the top to the bottom of the tank. Sliding up and down that road is a buoyant "donut" which sends a signal along the length of the rod. It's completely enclosed and simply. I've been using both the Cruz Pro gauge and the WEMA sending unit for 5 years with no problems whatsoever.

John Kalpus
S/V Prudence
Hull #15
San Diego, CA USA