Replacing Catalina 34 Diesel Fuel Tank

Replacing our Diesel Fuel Tank

I repaired our fuel tank in 2017 using JB Weld Marine putty to cure a leak from the welded outboard lower edge of the tank, it has held to this day - Nov. 11th 2025 

This weekend after a day of light sailing, I found fuel on the Puppy Pad that we keep on the inside of the hull below the tank. Dang!

Looking deeper, there was fuel residue all down the inside of the hull and into the aft most bilge. Luckily it had not reached the level of the limber hole between the aft and middle bilge - so there was nothing to pump overboard .. Phew!

The tank is OEM from 1987, time to replace it.

Step 1: Drain the tank. I disconnected the fuel pipe from the output of the Facet Fuel pump and replaced it with a 24" piece of 3/8" hose the other end in a 5 gallon Jerry can ( I only had Gas Cans empty, so I tied a piece of string to the can handle to highlight that it was not Gasoline !! )

With the 'ignition' key on, I could turn the fuel pump on and off from inside the cabin by using the master engine control key on the cabin control panel.

It took about 20 minutes to empty the rest of the fuel from the tank. I filled the 1st 5 gallon tank, turned the pump off, swapped to the next 5 gallon tank and turned the pump back on. Total of about 6 gallons drained.

I could replace the tank with something different, but really want to keep the boat in the best condition so we're splurging and replacing the tank with a new one from Catalina Direct. Calling CD and speaking with Kevin ( he's always very helpful ), he advised that I should measure the tank to confirm that the replacement will fit. So, time to pull the Tank.

The tank is located at the foot of the aft berth behind the plywood bulkhead on the Port side. After pulling everything out of the garage ( our nickname for the aft berth ) it took only a few minutes to remove the dozen or so screws and pull out the bulkhead. Then disconnect the Fuel Fill hose, Fuel Vent hose, Fuel Supply hose ( had to cut that, just could not get the hose off of the connection ) , the Fuel Return hose and the Electrical connection for the Tank Sensor ( had to cut those too. Luckily I had anticipated that I might have to remove the tank in the future and had left some slack in the tank sensor wiring). Finally remove the two ground wires attached to the top ground strap. 

To remove the tank, there are 6 screws on the forward end of the tank that secure it to the shelf on which the tank sits.

With all that done, it's just a case of sliding the tank to starboard and into the aft berth. Once it's in the berth, then, standing at the entrance to the berth, the tank can be manhandled and placed on the galley counter ( over the sinks ), from there, it's just a case of moving it to the cabin steps and managing it onto the cockpit deck. The tank is not particularly heavy, but it is awkward.

With the tank at home, I got my tape measure out and verified the dimensions.

This drawing is an edit of the one provided by Catalina Direct. Note their drawing is not 'complete' I guess they don't want to provide all of the dimensions for sales reasons.

Our tank dimensions are in Red plus the fill and vent pipe connections are shown in my version.

Catalina Direct have been a great resource for getting stuff done on Eximius, and they are always very helpful. That's particularly important with the recent loss of the Catalina Factory - at least, it looks like the factory is going away unless they can find someone to take it over - PLEASE - but note! Catalina Direct is not any part of Catalina Yachts. 

Ok, I have sent my drawing to CD and should hear back from them today confirming the dimensions and the inclusion of the Fuel Vent and Fill pipes. As soon as they do, I'll place the order.

CD also sells some underlayment strips to increase aeration beneath the tank to reduce the risk of future corrosion, so the new tank should last another 30 years ( that will be 2055 ). By all means, come back then and see if there has been an update. 😉

So, the tank should arrive in about a week - we're a dock queen till then. I could install a temporary tank but a week is not a big deal.

Meanwhile: With the tank out and the aft berth empty, I can do a few things.

• Clean up the tank support shelf
• Clean up the inside of the hull from the shelf area all the way down to the aft bilge. 
• Both of these require plenty of cleaning, degreasing, I may even get the bilge paint out, not necessary but would be nice.
• Clean up the inside of the under sink cupboard in the head.

The tank has certainly got a healthy growth of Diesel Bug, the new tank will be virgin clean but the supply hose is probably infected, so a new hose is in my future.

The Forward end of the new tank has a tab for screwing down to the support shelf but there is no tab on the aft end of the tank ( narrow end ) but the fuel fill hose is very rigid and should prevent the tank moving but I think I'll add a hold down strap all the same.

While at it, I'll do some general cleaning hopefully to reduce the diesel smell in the cabin.

New tank is ordered, just waiting to confirm the shipping cost.

Stay tuned.

See you on the water - when the new tank is installed.

Paul