Polyethylene permanent fuel tank modification

I came by a 17 gallon permanent fuel tank at a swap meet for a price too good to pass up in a size that will just barely fit my boat. The problem I found when sizing it up against the spaces in my boat that would accommodate it is the fill neck and vent are molded into the top of the tank, and there won't be enough space above the tank to complete the fuel neck.

I'm inclined to just cut the neck off, plug the area with a plate & gasket and drill a hole elsewhere and install a flush flange with a venting screw cap (something like this https://www.ebay.com/itm/JAZ-6-Bolt-Flange-Fuel-Cell-Filler-Plate-Kit-P-N-350-201-06/292652644372?epid=663430398&hash=item442374f814%3Ag%3AwzEAAOSwD9pbVkJ9&_nkw=fuel+tank+flange&rt=nc), but before I do all this I wasn't sure if there's anything I should be concerned about that I'm not thinking of.

When finished the plan would be for it to be in a vented compartment below the rear deck permanently attached to the hull with the std. gas tank retainers. I would open a hatch cover to gain access to the fill cap.

Problem as I see it will be achieving a good seal. Polyethylene and other polymers really expand and contract with temperature. Like when using Starboard or other super plastics, if using an 1/8" bolt or screw, they advise using a 1/4" hole, as that is how much potentially the material can move.

Don't know your specific layout, but I'd see if there was another orientation in which to mount it, else you might need to make some permanent structure on the deck above the fuel fill/vent - like a jump seat or electronics pod - that would protect that area and still allow you to use the OEM configuration.

Unfortunately I'm trying to fit a square peg in a round hole with this one and might be better off letting the 17 gallon go and buying a 12 gallon even though I'd rather have the extended range now that Champlain is on my hit list of lakes to be fishing as often as I can.

The tank is slightly longer than the cavity I have for it, so I would need to notch the foam out a few inches just to accommodate the tank with the longest side of the tank running lengthwise with the boat. This configuration would give me plenty of room for the starting battery in the rear compartment along with a 17" x 15" storage area but it would restrict my access to the drain plug and other plumbing at the base of the transom.

If I turn the tank so the long side runs perpendicular to the keel-line of the boat fitting the starting battery alongside it will be a tight squeeze and the storage bin will get trimmed down to about 8" x 15" and the restricted access to the transom plumbing will be worse.

In either configuration there won't be sufficient clearance for the neck to connect to a pipe section of sufficient length to allow a pump to fit into it and not splash back when being filled. Any fill point I add to the deck above the tank will need to make a 90 degree turn over to the tank just below the cap flange, two 90 degree turns if I have the long side of the tank perpendicular to the center line of the boat.

See PM

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Looks like I should be able to change up the design and put the tank in the front of the boat. I should have just enough space to fit this deck-mounted fuel fill above it.


https://www.amazon.com/gp/product/B001BWE9MG/ref=ox_sc_saved_title_3?smid=ATVPDKIKX0DER&psc=1

onthewater102 said:

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Click to expand...

I sent you a PM with pricing on permanent fuel tanks I can get at a discount ...