I have a 1989 C36 and had to replace the fuel tank about 2 years ago. A friend with a 1988 C36 had to replace his last summer. Based on our failures, and the ones you mention, it seems likely you may also face a failure.

My tank started to leak through pin holes corroded in the bottom of the tank. The tank sits directly on plywood, and evidently there is enough moisture, lack of oxygen, acid from the wood, or something to cause local corrosion cells. I did not discover the problem right away, but the boat had a terrible diesel smell that could not be eliminated, probably because the tiny leaks saturated the plywood, but evaporated before becoming visible. Eventially, the leak became large enough to leak into the bilge. I discovered the leak while the boat was hauled for bottom painting.

I explored several options, but in the end found that Catalina sells exact replacement tanks made out of a thicker aluminum for a fairly reasonable price. They shipped the new tank with plastic strips to space the tank away from the wood and provide ventilation.

While I had the fuel tank out, I replaced the water heater as well. I figured after 20 years it could not last too much longer, and it was readily removed with the fuel tank out.

Gary Teeter
AnnieG
Everett, WA
Hull 966

My boat is an 88 model, the tank was replaced after survey when I purchased it. The tank is fairly easy to change on the MKI boats. If you replace the tank please take some pictures as you procede.

As for corrosion from the tank sitting on a plywood base, I do not know. My assumption is that the corrosion starts on the inside of the tank, if you have water present in your fuel it settles to the bottom of the tank just like it does in your fuel filter bowl as the fuel is lighter than water.

Ted,
There is an excellent article on the website describing one of the first fuel tank replacements in a C36. It was written by Thom Reeves and Doug Smith. If you look under the Technical Tab on the home page you should find it, or you can do a search. In their case, the corrosion started from the outside (possibly from exposed nail heads?!?). After I read the article, I took my tank out to inspect the bottom, but it looked in fine shape. I don't think you can make a blanket statement that all C36 MkI tanks will develope leaks.

Ted,

It could be operator error, but when I looked in the Association Member List just now I couldn't find your name. Alas, in order to access the C36IA's extensive Upgrades and Maintenance libraries you'll need to be a Member of the Association. Let me just say, It's worth it!

Here's the link to sign up. [URL="http://www.c36ia.com/?q=node/25"]http://www.c36ia.com/?q=node/25[/URL]

The 3-year deal is the best, first because you automatically will receive a CD archive of past Tech Notes, which is a GREAT resource to have on your boat, especially when you're away from internet service. And second, because the price is right. And third, because it saves you the hassle of having to re-sign up each year.

We would love to have you aboard.

Just curious, what is the cost of the MK I fuel tank? I'm on a crusade to upgrade and lower the effective age of my '91 MK I and this preventive maintenance item could make the list.

I could not find my receipt so it must be on the boat. As I recall in 2007 the tank cost a little over $400. The new tank came with a new level sender installed, and instructions for blocking the new tank into position.

The corrosion definitely came from outside the tank. White powdery aluminum oxide covered several areas of the tank bottom. When I cleaned it off, several areas were pretty deeply corroded. It did not seem to be associated with nail heads or other point sources.

Gary Teeter
AnnieG
Hull 966
Everett WA

Thanks Gary.

Jan 2005 I purchased a new fuel tank for Gone With The Wind. Cost $280.50 for the tank and $30.64 for shipping from CA to ME. I believe the part # for the MK1 is 50008. It came with a new sending unit the plywood platform and material to hold the tank off of the plywood.
I believe the corrision starts on the outside because if you are on salt water more than likely you will have some of the water get between the plywood and the tank and it will just sit and eventually corrode the aluminum. I addressed this with putting automoble undercoating all around the bottom of the tank. Time will tell is this was a good thing to do or not. I believe boats in freshwater will more than likely not have an issue and do not believe moisture from the inside could cause the corrision as the fuel is in motion on the boat inside the tank. (just my opinion!)

I believe the ABYC recommends a layer of neoprene be glued to the bottom of the tank to help with corrosion issues. I don't actually see how this could help, but my surveyor was quite concerned that I didn't have it when I bought my boat. Time will tell because I don't foresee pulling the tank out any time soon - the tank was replaced a few years back.

Has Catalina moved their parts dept to Florida? I live about 3 blocks from the Woodland Hills factory and could save on shipping.

I had the pin hole problem from the bottom of the tank sitting in water. This was within a year of the boat being new. Mr Butler gave me a new tank at cost. I made a platform covered with epoxy and placed a plastic (?or rubber) mat that sat up off the base. I also coated the bottom of the new fuel tank with epoxy. its lasted for more then 22 years now.

Gary
Did you find that you also had to replace any of the fuel lines when you replaced your fuel tank?