Fuel Tank Liner?

[starfish]

Hello forum,

After a couple rough weather days, my engine has started to flutter. Replaced the fuel filter, did not notice any obstruction or diesel bug issues but a local mechanic at the marina I was towed into says my fuel tank liner has disintegrated. I have NEVER heard of the tank having a liner. Has anyone heard of this and has experience in dealing with this situation?

Thanks very much for your attention.

Ed
Starfish #333

[ElizabethG]

Hi Ed,

I pulled this from ChatGPT.....Can't vouch for the accuracy and I ran it for a 2004 model.


Short answer: **No — the aluminum diesel fuel tanks used in early-2000s Catalina sailboats (including your 2004) were *not* lined.**

### Details specific to Catalina (circa 2004)

* Catalina typically used **marine-grade aluminum (usually 5052 or 5086)** fuel tanks.
* These tanks were **bare aluminum inside**, relying on:

* Aluminum’s natural oxide layer for corrosion resistance
* Clean diesel fuel (diesel is far less aggressive than gasoline)
* **No epoxy, phenolic, or polymer liner** was applied at the factory.

### Why Catalina didn’t use liners

* Liners can **fail, delaminate, or shed flakes**, which clog filters and injectors.
* Aluminum tanks with **good fuel hygiene** have a very long service life.
* Liners can actually **trap moisture** against aluminum and *accelerate corrosion* if they fail.

### What *is* common (and often mistaken for a liner)

* **Dark staining or varnish** from aged diesel
* **Biofilm / microbial growth** (diesel bug)
* Light gray or dull appearance from aluminum oxidation

None of those indicate a factory liner.

### What *can* cause problems in Catalina aluminum tanks

Given the age of your boat, the usual issues are:

* **Water sitting against the bottom of the tank**
* **Microbial growth producing acids**
* **External corrosion** where the tank contacts:

* Wet foam
* Bilge water
* Treated wood or dissimilar metals

Catalina tanks were often **foamed or tightly boxed in**, which is the *real* long-term risk—not the lack of a liner.

### When a liner *might* exist

Only if:

* A **previous owner had the tank relined** (rare, and usually a last resort)
* The tank was **replaced aftermarket**

If you want to confirm absolutely:

* Remove the **fuel sender** and inspect inside with:

* A flashlight + mirror
* Or a borescope
Bare aluminum will look metallic (even if stained), not painted or glossy.

---

If you’d like, I can also help you:

* Assess whether your tank is at risk based on Catalina 350 layout
* Recommend inspection/maintenance steps
* Discuss when replacement is smarter than relining

[starfish]

Hi Elizabeth and thank you for the info. My boat is a 2005, not considered "early 2000's", do you think this applies to that year model?

Thanks
Ed

[ElizabethG]

Hi Ed,

I re-ran it for a 2005 and got the same answer...

Yes — the answer is the same for a 2005 Catalina 350 (including your specific year). Catalina used bare aluminum diesel fuel tanks in that model and year, and they do not have a factory internal liner.

[smcgauvran]

I have a 2006 Catalina 350 and I pulled the tank for a leak on a welded seam. The tank was aluminum--no liner.

It's easy to pull the fuel level sensor on the top of the tank and look inside. Best to do with less than 1/2 tank and a replacement gasket ready if needed.

[Olivia Mae]

I also have never heard of a liner in these tanks. Once upon a time, we could call Warren Pandy to find out, but sadly no more. There is how to article somewhere in the archives (maybe old mainsheet magazines on this site) about how to install a fuel polisher. This might be of interest to you. Our boat has one that a previous owner installed. I use it periodically just because I can and we've never had a fuel issue. Coincidence, probably, but I swear it works.