[C320-list] C320 Fuel Tank Replacement

[Allan S Field]

Jeff Hare has done a great write-up on this project.  Following is what I saved from his post, knowing that I'd eventually face this problem also.  Hope it helps!

The problem with this approach is that the drainage isn't directly to the bilge.  It will flow in front of the fuel tank and into the compartment where the aft water tank sits below the bunk.  Only when enough pools in there to rise to the hole where the water line joins into tank will it spill out and into the area where the prop shaft sits.  From there, it leads under the engine pan through a small drain hole.  Once under the engine pan area, this won't directly drain to the bilge cleanly since only if the boat is tilted forward will that space drain into the bilge.  Depending on how they finished the compartment holding the water tank, the fuel may bypass the prop shaft area and go directly below the engine pan once enough pools under the tank. So, my advice is not to do this as the result won't be great and it'll take quite a few rough sailing adventures to fully flush the stuff under the engine area out into the bilge for cleanup.

Instead you could consider some of these options:

- just use simple green on paper towels to wipe down the tank and as much of the area in front of the tank as you can reach.  This won't take care of cleaning the pool of diesel that the aft water tank may be sitting in.  That may eventually permeate the water tank, and if nothing else, keep your aft cabin smelling like a truck stop.  Not the best choice, but far better than trying to wash down the tank and collect the runoff in the bilge.

Best choice:
- remove the aft water tank and you'll be able to fully clean up the mess.
It's not all that difficult and could do it in an afternoon with a helper. 
  * To do this, drain the aft water tank (easy)
  * Disconnect the water line leading out of the tank which is right near the raw water strainer.  (easy)
  * Disconnect the water tank Fill hose and water tank vent line from the deck fill fitting and the overboard vent so that these ends are free.
(moderately easy)
  * Remove the two white wooden braces that hold the water tank down. (easy)
  * With a large wrench, unscrew the threaded fittings that connect the fill/vent hoses to the back of the water tank.  It's more difficult to remove the hoses from these fittings than it is to just unscrew them from the tank, while your assistant twists the hoses along with you from the area by the rudder post.  (bit of a pain in the neck, but not hard.  I did it by myself, and chose to replace the fill and vent hoses once I saw what they looked like).
  * At this point, the water tank will simply lift out and you can fully clean the area under the water tank (and the water tank itself) of diesel.
  * I used simple green full strength on wads of paper towels to mop up and clean out the area under the tank and just put them in plastic trash bag.

The net result here is that you'll end up being able to clean up the mold and mildew from under the aft cabin bunk at the same time.  I have pictures of before/after in ours.  

I'll also point out that our fuel tank ALSO showed signs of leaking out the fuel sender seal.  I was sure it was just the seal and people on this list convinced me to take a closer look before drawing this conclusion.  While this was indeed happening, there was a half-dime sized patch of corrosion that didn't even show when the tank was in place which was where the real leak was coming from.  It was leaking at a rate of about a tablespoon a week...sometimes.  Once I pulled the fuel tank, and put a flashlight on the corrosion spot outside the tank and looked inside the tank, I could see that the metal was extremely thin and could see the glowing of the flashlight.
Eventually it would have started gushing.  

It was confusing was that it didn't leak consistently.  At one point I had what seemed like a lot of fuel that had leaked, but then it appeared to stop which made me also think it was only leaking when the tank was full to the top.  

Your hull number is only 12 away from mine.  Many boats with much earlier hull numbers have already had corrosion leaks and I'd bet that most of them also showed wetness to some degree at the top of the tank around the cork seal for the sender.  Also, remember that it only takes a tiny errant piece of metal to roll under the tank and make contact  and you'll develop a galvanic corrosion leak after some time in a place you cannot inspect.

Ezell can deliver a new direct replacement tank pretty quickly (a week or
so) for about $425 that is made of significantly thicker metal and has a more high-tech sender and nice valves.  So it's worth considering.
Especially if you pull the old tank you'll be able to really clean up all traces of diesel.  

To drain our diesel tank (which was full) I simply used a cheap "drill pump"
from Home Depot that I put in my electric drill.  I disconnected the hose where it connects into the fuel filter and just pumped the fuel into some diesel fuel jugs.  Took about 20 min and the tank was really quite empty and lightweight at that point.  I don't know whether this little rotary pump was "diesel fuel" safe, but I had no problems with it whatsoever.

-----Original Message-----
From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of upwego
Sent: Monday, February 22, 2016 8:21 AM
To: C320 List <c320-list at lists.catalina320.com>
Subject: [C320-list] C320 Fuel Tank Replacement

I have just discovered a slow leak coming from underneath my fuel tank.  All the connection ports on top of the tank show no signs of leakage.  It may be a leak in the fuel tank itself. Has anyone experienced this condition and found another source of a leak that might be on the underside of the tank?  Has anyone removed and replaced a C320 fuel tank?  If so, any pointers that would be helpful or should I have it done be a mechanic?  I see Catalina Direct has a 29 gallon replacement for the 19.  Anyone tried upgrading to the larger tank?
Any advice or info would be helpful?
Thanks
Jack FitzgibbonHull #441, S/V wetted bliss