Leaking fuel tank

Stu Jackson · Jan 26, 2014

The fourth hose is the fuel return from the engine.

Haven't heard of any fiberglass tanks. All of our skippers replace with OEMs, although there have been some reports of our Mark II boats being built with fiberglass tanks. http://c34.org/bbs/index.php/topic,4085.msg23343.html#msg23343

Call Catalina in Florida and ask them.

Good luck.

PS scroll down to reply #27 in that link, it gives a source of the fiberglass tank!

dj2210 · Jan 26, 2014

Just replaced mine recently. The old tank had the manufacture's label on it. It was AFP and is now RDS in Florida. They still had the original drawings and made me a new tank for less than others. I called Catalina factory but they were having difficulty with getting the right part- go figure.

centerline · Jan 26, 2014

I have had great success with the por 15 tank sealer/liner.... i have used it on many tanks, large and small. it may be cheaper than a new tank, and if done correctly, will outlast a a new tank that is not lined with it.
but as with any epoxy, urethane, or paint type products, the prep work is the most important part.

the excess can be saved and used on other tanks in the future, which lowers the cost even more....

dj2210 · Jan 26, 2014

Gregory, yes I used a 5 in grinder/sander. It didn't take much to grind but it does make a mess. I decided not to fiberglass it in like the factory. Instead made some straps to go over the tank and bolted it to some blocks that are epoxied to the hull. This way if I need to take out the tank in the future it will be easy.

jrowan · Jan 27, 2014

gregorybross said:
I have diesel leaking into the bilge. After inspecting I can only conclude it is coming from the bottom of the tank. The tank appears to be the original aluminum tank. My boat is a 1996. It seams early for tank failure but I have a few questions for anyone who has replaced a fuel tank. First there are 4 hoses coming out of the top. The fill hose, vent hose, supply hose (with a valve ) and a 4th hose I cannot identify. A new tank from Catalina direct is $400. This is the oem aluminum tank . Does anyone know of a Fiberglas replacement that may resist corrosion better? Any helpful comments are much appreciated.
Greg

Greg, Before you go & pull out & replace your fuel tank are you positive that the tank is leaking? Because mine is over 30 years old on my original 1980 tank & it is holding fine (knock on fiberglass). Have you inserted a rag or paper or a sponge or something under the lowest area directly beneath the tank to confirm that is your leak source? Because the more common area of diesel leakage is from your fuel filter threaded connections not being tightened down, or clamps on the fuel lines being loose. There is a lot of vibration on everything connected to the engine that will manage to work itself loose over time. I would run your engine for an extended period of time under load, then check all clamps & hoses. It may just be a simple band clamp that is loose, & the leak may only be occurring when the engine is running & vibrating, making it harder to find the culprit.

Also check the seals around the injector pump, the fuel injectors, fuel lines & fuel filter housing first, & return lines before you pull your tank. Also in my opinion, I would stick with an aluminum OEM fuel tank if you do decide to replace it. Fiberglass tanks have been well known to get corroded from the corrosive nature of diesel & gas & can start to chemically break down over time. Google fiberglass fuel tank corrosion. Not sure if diesel is as corrosive as ethanol based higher octane gas is, but since the aluminum tanks have a 30+ lifespan, I would stick to what works. My 2 cents.

dj2210 · Jan 28, 2014

My tank was leaking ever so slightly at the bottom weld where the tang or corner was. The tank rests on the hull and the tabs are glassed in. I don't know if vibration and chafe was an issue but whatever causes leaks in aluminum tanks I decided it was just easier to replace.

pencema · Mar 14, 2014

dj2210 said:
My tank was leaking ever so slightly at the bottom weld where the tang or corner was. The tank rests on the hull and the tabs are glassed in. I don't know if vibration and chafe was an issue but whatever causes leaks in aluminum tanks I decided it was just easier to replace.

I've been getting oil in my bilge so I concluded the diesel tank must be leaking. I emptied it, pulled it and took it home for cleaning. I found no sign of leakage, and it held water over night. But going on 39 years, I decided I should replace the tank anyway, and I'm having a new one made locally.

Apparently in the early years there wasn't much standardization. My tank is rectangular, 36"x18"x7.5", and doesn't look like any of the pics I've seen posted. No hold-down tangs, just sat on a flat board at outboard end and a 2x4 block inboard. That block had collapsed and let the tank cant sideways, which helped convince me it was leaking.

Now I have to go leak-hunting again when the new tank goes in.

jrowan · Mar 17, 2014

pencema said:
I've been getting oil in my bilge so I concluded the diesel tank must be leaking. I emptied it, pulled it and took it home for cleaning. I found no sign of leakage, and it held water over night. But going on 39 years, I decided I should replace the tank anyway, and I'm having a new one made locally.

Apparently in the early years there wasn't much standardization. My tank is rectangular, 36"x18"x7.5", and doesn't look like any of the pics I've seen posted. No hold-down tangs, just sat on a flat board at outboard end and a 2x4 block inboard. That block had collapsed and let the tank cant sideways, which helped convince me it was leaking.

Now I have to go leak-hunting again when the new tank goes in.

Pencema,

If you're getting oil in your bilge then it is much more likely coming from a leaking oil filter seal, or from the engine seals being worn. The C-30 engine placement is good for even weight distribution being down low & centered in the hull, but it is famous for allowing bilge water to slosh around the bottom of the engine. Corrosion forms on the bottom of the oil pan & is well known to eventually rust out the oil pan. Inspect under the pan with a mirror. Or wipe under the pan with a clean rag. If you find a lot of oil clinging to the outside of the pan, it could have pin hole corrosion forming. Even if water doesn't actually slosh around & get the oil pan wet, condensation will naturally occur when the bilge water evaporates, & then condenses on the underside of the engine. I have known several C-30 owners who had to pull out there engines in order to replace the oil pan, which is a big job. Hopefully all you have is a loose oil filter, etc.
ps. Another place where oil can escape is the air return line which runs from the top of the valve cover back to the air filter housing. (This is how my 5411 is set up). The early Universal diesels were set up this way, but I'm not sure if the later M25 engines have this "feature."

Brad Woodward · Mar 19, 2014

I think many tanks don't last as long as others is due to water in the tank that isn't cleaned out. The pick up is off the bottom a little and won't get it unless the water gets deep enough but then will always leave some there. You will find it it the water separator. One reason you get a lot of water in the tank is not keeping the tank full as much as possible. Leaving a tank less than 2/3s full, especially in cool damp weather will allow condensation to build up inside the tank and collect in the bottom. Believe it or not, alga will also grow in the diesel too. Keeping your tank full most of the time will keep your tank from corroding as quickly. You will have fewer dirty fuel problems as well.

Leaking fuel tank

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