Fuel Tank Replacement

[Mike and Theresa Vaccaro]

When we removed our fuel tank for cleaning, we found that we pitting corrosion on the bottom.  This is about the most serious form of corrosion in aluminum sheet, and the only proper repair is replacement of the metal.  Turns out that the only thing that was preventing the tank from leaking prior to removal was the crud on the bottom!  It was effectively blocking the small pin holes that formed as a result of corrosion.  This is not to say that Ron's recommendation to remove the tank for cleaning at regular intervals of about 5 years is not correct!  If you don't clean the tank, you may have difficulty running the engine.  It's unfortunate that the tank corroded, but over 15 years in a salt water environment with no maintenance whatsoever is bound to lead to trouble.

The replacement tank we ordered from Catalina is better than the old tank.  The quality of the welding is much better, it comes as a complete unit (sender and pick-ups installed), and is made out of thicker 5052 alloy (the old tank was .080 and the new tank is .125).  Cost for the new tank was 250 dollars and included shipping.  

I spoke to a local airframe mechanic who is an experienced aluminum welder and he recommended replacement vs. repair, since a proper repair to the old tank would require removal of the entire bottom and replacement, especially considering the reasonable cost of replacement.  

I also inquired with Catalina as to the availability of a plastic tank--they indicated that proper tank for our boat was aluminum.  There was a previous post regarding a plastic replacement.  I wasn't able to obtain a definitive answer from the factory (they indicated that the C-36 uses a plastic tank), but that may be an option as well.  

The new tank has slightly different dimensions than the old.  It requires new lag bolts for mounting, and I drilled additional holes in the flange on the tank for this purpose and used 1/4" X 1" lag bolts with washers.  I didn't use the outboard hole drilled at the factory, as it was too close to the hull for comfort.  Additionally, the new tank's vent connection is about 5" farther forward than the old, so a replacement for the vent line was required as well.  The ground location is moved forward as well, so I spliced in a new "harness" for the tank.

We also replaced all of the fuel hose and clamps (many of the old ones were so corroded they simply snapped off), and the primary fuel filter.  Had a bit of trouble getting the new system bled and properly pressurized (had a recalcitrant air bubble somewhere that simply refused to go away), but after cracking the injectors, we finally got everything working normally.

Like most of the other projects, not too difficult, took twice as long as planned, and included the cost of a new tank--which we hadn't planned on.  The biggest lesson learned is to keep the system clean with regular maintenance, and hopefully it won't every have to be replaced en mass!

We'll post some pictures to the project page when we get a chance.

Cheers,

Mike

[Ran139]

Mike,

  Thanks for the post on the fuel tank. My boat is a year older than yours and repalcing the tank is on my project list. I look forward to seeing the pictures.

  Fair Winds,

  Ran

[Mike and Theresa Vaccaro]

Ron,

One thing I forgot to mention--when we first removed the tank, the bottom looked the best, except for a small area of pitting.  This can be detected visually, but the total extent of the corrosion cannot.  Additionally, the pits on the outside of the metal are like the tip of an iceberg--most of the damage lies under the surface.  The way we found out the true extent of the damage was during the LEAK CHECK.  So the lesson learned is DO A LEAK CHECK PRIOR TO RE-INSTALLING THE TANK IN THE BOAT (it can save a bit of work!).  Seems obvious, after the fact!  

It's not really necessary to pressure check the tank (and don't use more than 2-3 PSI if you do), just fill it with fuel or water with dye and check for leaks.

This technique will also serve to expose weeping cracks in the weld.  A weld crack can normally be repaired with epoxy.

Cheers,

Mike

[Ed Shankle]

Just finished doing the same project; replacing the fuel tank and had to do all the same retrofits. One additional item I'd add to Mike's comments is to specify the fittings sizes to Catalina when ordering the tank. I didn't think of it and it came with two identical sized barbed end fittings for the hoses. Trouble is, the fuel line is 3/8's and the return line in 1/4 on TailWind. I couldn't find the right combinations of fittings locally to fix, so I called Catalina, who ultimately supplied them to me. (which of course delayed the whole process)
Also, the fittings provided are aluminum, so be careful if you change over; as we have discussed with the transmission drain plug, alumimum strips easily.
Finally, be sure to use a thread sealer on the fittings.

Ed

[Ed Shankle]

Ron,
That's what I intended to do, however, Catalina has changed the diameter of the threaded opening to the tank. It required new hardware, which they provided, installed.

Ed

[Mike and Theresa Vaccaro]

One other thing to consider is dissimilar metal corrosion.  As someone who lost a tank to corrosion, I'd certainly stick with all aluminum fittings!

Another option is to use a small 3/8" ID hose off the nipple on the tank and then make a brass "reducer" and connect that to the 1/4" ID return line.  This eliminates the problem with dissimilar metal, but obvious adds a new potential leak point!  The best option is to order the proper fittings if time and circumstances permit.

Ron also brings up a great point:  never throw the old part away until the new one is installed!  Even "identical" replacement parts can have evolutionary improvements that make 'em just different enough that you've got some engineering to do.  Having the old parts on hand usually makes this process somewhat easier.

Permatex Type 2 makes a great non-hardening thread sealant for fuel systems.  Although it's been said before:  silicone and teflon tape have no place in a fuel system.

Cheers,

Mike

[Mike and Theresa Vaccaro]

Ron,

You bet...haven't had an original thought in 41 years and see no reason to start at this point!

Cheers,

Mike

[Ted Pounds]

Mike,

Who did you talk to at Catalina to order the tank?  I just got off the phone with parts and they quoted me a price of $313 plus shipping.  What part number did you use?  The part number they gave me was 20791.  

Thanks,
Ted

[Mike and Theresa Vaccaro]

Ted,

Just pulled the invoice (dated 7 Jun 04).  Part number is the same (20791) and description is "Unit Fuel Aluminum C34/C36 #31" and the unit price is 255.00.  Shipping was 23.99.  Spoke to the lady that works with Robert in parts (don't recall her name).  

Seems odd that they'd raise the price, but could be a new batch of tanks???

Best of Luck,

Mike

[Ed Shankle]

I had the same experience. They quoted me $313, but invoiced me $255.
Maybe it has something to do with changing from plastic back to aluminum? Shipping was also @$25.

Ed