Not much posting going on lately, so here's one that might be of interest. The original 48ish gal aluminum fuel tank in Skookum developed a pinhole leak in Dec 2021. Discovered a bilge full of diesel on a boat check one weekend. Bummer.
Fortuna smiled upon me and the Coast Guard, because when I'd replaced her tiny bilge pump with stacked sipper and high-capacity bilge pumps years ago, I opted for the Water Witch bilge pump switches--they work on conductivity rather than level, and so they retained the fuel rather than pumping it into the bay. I recommend them!
After cleaning out the mess in the bilge and sucking out what was left in the tank (what a hassle), we all know from the archives that you have to cut that tank out of there unless you're up for engine removal. Diesel's not particularly ignitable, but I like a belt AND suspenders, so I rented a 4-gas meter for the weekend. Got into the port coffin and confirmed that the LEL was less than 2% and then inerted the tank to 6% oxygen with a small CO2 cylinder I had for beer brewing. Then I put the sawzall to it while my neighbor stood by with a fire extinguisher and "9-1-" dialed on his cell--a bit of excitement!
All good though. I'd mocked up dimensions in cardboard using the old FL Tanks drawings from our site, but found it just a bitch to get them in side by side without removing more underdeck steering hardware. So I shortened a half an inch in a couple dimensions then waited a couple months for delivery of two half-tanks.
To head off a future leak, I found some trim PVC strip at Lowes and made standoffs to keep the tank off the wooden framing, see the photo of gluing them in. Two tanks required a very spendy 6-port bronze valve for fuel delivery and return, and big ol 3-way for the fill. I replaced the original tank gauge view port with a removable 6" deck plate, for easy access to the valves. I looked into spending more on the 90 NPT to hose barb fittings, but decided it was probably minimal additional fire risk to go with poly for those. Your results may vary. The fabricator ignored my request for a separate NPT hole for the diesel furnace in the starboard tank, so I put in a tee in the vent line for the furnace to sip out of.
Securing the tanks with a fixed strap with rubber liner seemed dumb, so I went with some SS ratchet straps, 600 lb rated. Because the two tanks will sag towards the centerline of the boat, I put a little post under the center of the one wooden crossmember and for securement of the tanks, one strap per tank goes all the way around the inside and pulls it securely outboard, while the two hold-downs across them both look likely to withstand a rollover.
Monitoring two tanks, I went with one gauge and a rocker switch, making new use of a useless original engine control panel in the starboard lazarette wall.
So, a successful but time-consuming little project, letting me get back to gunkholing instead of major reconstruction. Hope this gives someone else an idea of what to do/not do.
Merry Christmas!