... My 26 year old 47 gallon fuel tank seems perfectly fine, it’s location under the QB berth is dry, and assuming corrosion free. I’m hoping it’ll come out easily. I’m installing a new polishing system, which means new fittings drilled into the access plate (which I have wanted to replace for some time), the tank or installing a second plate with fittings ... I’d rather not install fittings & tubes in access plates. The more I think about this, with the work I’ll have to do plus clean the tank anyway, I’m thinking replacing the tank would be a good idea, maybe it’ll last another 26 years, maybe it fails next year. That way I get exactly what I want, with fittings exactly where I want them. I’m optimistic the original stock tank can be enlarged 10% or more to give me added capacity, and conform better to the hull shape.

Triple M Plastics in Maine builds nice polypropylene tanks for custom boats at Lyman Morse, 3/8” wall material, ½” lids, pressure tested, they say for some tanks they don’t even install access plates because nothing sticks to the plastic, if you pick up bad fuel, remove a fitting and flush it out (I’d probably still go with an access plate). Poly tanks are becoming more common although many builders won’t do it for liability reasons. I like the idea of a poly tank, my water & holding tanks were recent custom molded poly builds, but the cost in my case is some 40% more and it’ll weigh 20% more (thicker material and poly tanks require many more baffles). Being translucent probably won’t help me that much under the plywood, under the berth.

There are plenty of good aluminum fabricators, prices more competitive, the material used today (.125”) thicker than mine of 25 years vintage (.09”), and if I go the custom route as opposed to the stock one I have, I’m sure to get a more durable tank that should last a long time. Have I missed any more pros & cons of poly vs. aluminum ? I guess if I have a problem in the middle of nowhere, an aluminum welder will be easier to find.

I saw MaineSail’s excellent post for replacing a fuel tank and will use many of his suggestions – THANKS MaineSail ! If I chose aluminum, I’ll have an 8” square access plate over a 6” opening centered over one baffle so I can get in to clean all surfaces, with 5/16” or 3/8” bolts welded to backing bars, 12 of them will secure the plate with flat & lock washers & nuts over a 1/8” BUNA-N gasket. All fittings will be aluminum with shut-offs on the outlets, all on top of the tank, I’ll use Loctite 592 or Megaloc for a sealant, my Fill will extend down the inside of the tank to reduce foaming. My pick-up tubes will be copper or nylon, all of them cut at a slight angle, ¼” or so off the bottom, with no screens … same for the drops, and secured / bracketed to the tank bottom. The pick-up and drop for the polisher as far apart as possible. Will also include a spare pick-up & drop fitting for future heater or whatever capped off for now, and install my existing electronic sender, with a stamped plate welded underneath for fasteners, drilled & tapped.

I wonder if I should bother priming and epoxy-painting an aluminum tank ? I may rest the tank on neoprene, or I might foam it in, fully supporting the bottom ? And does an aluminum tank need to be grounded ?

Did I forget anything ?

Thanks, cheers, John