[C320-list] Plastic Fuel Tank

[Jeff Hare]

Hi Jeff,

The tank I had Ezell build was a modified from the original Catalina design. The pickup port was moved closer towards the center forward corner, and the tank volume was increased. It had a center side to side baffle I believe and used thicker aluminum than the factory tank. The fill port was moved slightly to encourage the "wash down" effect of flushing tank sediment towards the fuel pickup during fill. There is not a lot of reason for cleanout ports in the C320 tank if you use clean fuel, keep a tiny amount of biocide in the fuel (many marine fuel stations that have high turnover of fuel have this added anyway in my experience). When we pulled our tank after 14 years, internal inspection showed very little inside debris. Maybe if you use a lot of crappy fuel and no biocide, and have your boat sit stagnant for long periods of time, your tank might get gunked up and need to be cleaned.

As you mentioned, I lightly scuffed the bottom/side tank surfaces, masked it off and rolled on a few coats of truck bed liner to the bottom. The original factory tank was sitting on a couple scraps of the rub-rail that were duck taped to the bottom. I think I used thin Ipe wood cleats with some rubber padding aligned in a way that didn't trap any water under the tank when installing the new one.

Generally speaking, the holes tend to originate from inside the tank or anywhere a stray bolt or flake of metal might wedge against the side of the tank. I chose to add a barrier coat to guard against a stray screw or something metal rolling up against the tank.

The inside and aft side chock cleats that held the tank in place were removed and new mounting cleats were placed to accommodate the larger tank.

I think this tank could still use a float style analog fuel gauge (which I prefer over the digital version). The digital version seems to register changes abruptly in 1/8 (maybe 1/4?) tank increments whereas the analog sender sweeps over a full range like I'd expect. I like gradual fuel gauge changes.

While the tank is out, it's a great time to replace the aft water tank fill and vent hoses, yank out the ridiculous and totally useless blower vent hoses and put screen over the transom vent holes so the system can actually breath.

The new tank fits through the aft cabin door and through the access port by the fridge compressor (after removing the access door trim).  It'll fit behind the rudder post after disconnecting the cockpit scupper hoses. (Replace those black and clear spiral hoses as you'll find that they are very brittle and will simply crack open up if you bend them).

While the tank is out, it's a great time to wipe down the area with a cleaner and slap in a coat of white Interlux Bilgekote in that aft locker.  

I did remove the aft shelf while doing this project. When reassembling the whole thing, it's also a good time to fit some Eye straps to the inboard edge of the shelf so that you can attach a cargo net to prevent stuff in the starboard aft locker from falling off the shelf towards the rudder post/quadrant.

My design added ~5" of extra tank width to the inboard edge and maybe a little bit of length to the foreward edge. It used .125 Aluminum (the older tanks used .090).  My new tank cost $325 plus shipping in Aug 2015. That was the price for the tank built to my new design. At the time, the smaller stock tank retailed through Ezell for $420.

I haven't checked to see what my larger 23 gal tank costs to build today but it'll almost certainly be LESS than the smaller stock factory tank. You'd have to work through me (because the designer of the tank 'owns' the design and sets the retail price). That's why the Stock tank costs much less to manufacture than they charge for a Catalina tank (as I recall). Meaning that Catalina sets the retail price and takes a cut since it's their tank design.

I did a full scale mockup of the tank with Luan plywood to test fit the design and be sure I could get it through all the places it needed to get through and be able to drop into place using as few bad words as possible.

-Jeff Hare
C355 #17 Solstice
Formerly #809 Woodbine II (now Mark Hood's S/V Dodger)

-----Original Message-----
From: C320-list <c320-list-bounces at lists.catalina320.com> On Behalf Of Jeff Smith via C320-list
Sent: Friday, February 24, 2023 9:32 AM
To: c320-list at lists.catalina320.com
Cc: Jeff Smith <svsailmates512 at gmail.com>
Subject: [C320-list] Plastic Fuel Tank

To all,

Has anyone replaced their fuel tank with a plastic tank? I have my tank out and had planned to replace it with an Ezell with no baffles and an inspection port. I was corresponding with the factory on a different matter (Warren Pandy), and he indicated that going without a baffle may not be a good thing. He suggested just recoating my tank (it is not currently leaking) and making sure I keep it elevated while in the boat.

So, now I am second guessing the Ezell order and thought about a plastic tank as a possible option. The other option is that I could cut my current tank and install two clean-out ports to clean on both sides of the baffle (recoating it like Jeff Hare did using bedliner spray paint). But, the front port would be a one-time use only, because it would not be accessible in the boat.

Any thoughts?
Jeff, ’94 #121