MK-II FUEL TANK CLEANING

By Tom Assenmacher
(1975 yawl SHEARWATER)

 

We had not cleaned the fuel tank on our A-37 yawl since we bought her in 1982 (and it hadn’t been cleaned before we bought her).  After completing the 2002 engine replacement and general refurbishment of SHEARWATER, we didn’t get around to giving the fuel tank a much needed cleaning until late this summer (probably because we dreaded the job).  Finally, in anticipation of perhaps some extended cruising in the near future, we decided to “bite the bullet” and do the job.

 

 (Recently, Joran Gendell  sent the following photo of sludge he collected from the bottom of the fuel tank on ELIXIR which should be enough incentive to do the job on YOUR tank! However, we didn't find nearly this much "CRUD" in SHEARWATER's tank.)

 


Sludge Found in ELIXIR's Fuel Tank

 

 

 The following is roughly what we did:

-          Preparation for tank removal: (Although the tank COULD be cleaned in-place, we decided it would be much easier to clean the tank if we removed the tank from the bilge.) In order to gain access to the fuel tank, we removed the outboard part of the “L” section of the port settee. This is easily done by removing about a dozen screws and the assembly simply lifts out.  We then removed the house batteries that we have installed in this areas and set all items aside outside the boat. As we had installed an electric fuel “boost” pump (with a “T”, shutoff valve, and length of fuel line hose in the line) as part of the new engine installation, we simply turned on the pump, opened the valve and pumped all but about 2 gallons of “old” diesel fuel from the tank. Once we had most of the fuel removed, we then removed the access panel screws and removed the access panel and set it aside.

 

Fuel Tank Access Panel (Top Side)

 

 

 

We were then able to see the inside of the tank for the first time in 28 years!

 

 

View of Fuel Tank Interior (Note Installed Baffle)

 We also removed the sheet metal screws which secure (sort of) the fuel tank to the floor pan.  To remove the remainder of the fuel, we used a wet/dry shopvac with a length of ½” PVC pipe attached to the end of the vacuum hose (we used a long piece of vacuum hose, with the shopvac on the dock.  There was about ½” of black ‘sludgy’ stuff in the bottom of the tank.

 

 

Removing Residual Fuel from Tank Using PVC Pipe Attached to ShopVac

 

- Tank removal: The tank (with the access panel and tank attachment screws removed) simply lifts out of the bilge area.  We did not actually remove the tank from the boat (not sure if it would pass through the companionway – it would be a close fit), but sat it on the cabin floor for further work and cleaning.

 

 

 

Fuel Tank Removed from Bilge Area

 

Make sure you have a lot of padding and rags available if you plan to work on the tank onboard the boat.

 

 

- Tank cleaning:  Since the tank appeared to be in relatively good condition, we used an industrial (water soluble-used in pressure washers) degreaser full strength to remove the “crud” in the tank.  We sloshed this around inside the tank with an old mop and scrub brush, and vacuumed out the dirty cleaner and “crud”. 

 

 

Ready to Clean Fuel Tank with Scrub Brush (Note: Use Waterproof Gloves)

 

There were some areas on the bottom that were hard and crusty, which were easily removed with a putty knife (the bottom of the tank is just within arm reach).   We flushed the tank several times with clean water (again using the shopvac to remove the water) and allowed the tank to dry overnight.

 

 

- Tank inspection: We had envisioned some pitting of the aluminum tank, but a thorough inspection revealed no pitting on the inside of the tank, and were pleasantly surprised to find only very superficial pitting on the outside (it appeared that at one time there may have been some water in the bilge at the lower level of the tank).

 

 

Fuel Tank Showing Minor Exterior Pitting

 

 One of the reasons to remove the tank is to inspect tank exterior and to clean the bilge area.  We found several small tools and debris lying in the bilge area (wood chisel, screws, etc.). 

 

Bilge Area After Fuel Tank Was Removed

 

 

We inspected the tank access plate for excessive corrosion (there is some around the bronze pipe fittings, but not serious), and checked the engine fuel intake pipe (piece of copper tubing soldered to a bronze “street ell” which extends to within about 1.5” of the bottom) for integrity and corrosion.

 

 

Fuel Tank Access Panel Showing Fuel Intake Pipe

 

We also inspected the fuel return line, fuel vent, etc. for condition and security.

 

 

All Fuel Tank Hoses Installed and Secured

 

 

- Reassembly and installation:  Reassembly was basically the reversal of the tank removal.  We fabricated a new gasket for the tank access plate using rubberized cork gasket material available from your local NAPA auto parts store (it comes in a roll and is wide enough that piecing of the gasket is unnecessary).  We used “anti-seize” compound on the access panel screws to ensure against corrosion and seizing.  We lowered the assembled tank into the bilge area and reattached the tank mounting screws.  Since these mounting screws are only screwed through the thin fiberglass flange of the floor pan, we decided to add some strengthening in order to keep the tank from shifting under less than optimal conditions.  We fabricated 1.25” square cleats that surrounded the periphery of the tank and secured the cleats to the walls of the tank area floor pan with large SS sheet metal screws, making for a much more robust assembly.

 

 

Final Installation with All Lines Connected (Note Wooden Battens for Security)

 

We then reconnected all fuel lines, and connected the tank bonding wires, refilled the tank and checked the engine operation (self bleeding system).  We are now confident that we have a CLEAN fuel system.