This is a cautionary tale of diesel, lumpy seas and fuel tanks which, like Tutankhamun's tomb, had not been opened in an exceedingly long time.

The story of the transit to Land's End will be covered in another blog post but this post specifically deals with the effects of 'tainted'- to put it politely - fuel. To cut the story slightly short we had left Penzance shortly after 0700 having anchored overnight and made good progress south to the coast, touching 8 kts on the tide. Turning West we slowed and made torturous progress towards 'Longships' at Land's End. I turned in for an hour or so after a long night of 3 hour watches on anchor and about 1 hour in the skipper opened up the hatch to the cargo area and shouted the engine was misbehaving.

I quickly donned my work gear and headed to the engine room. The prefilter had a small amount of gunk in the bottom of it, but nowhere near the amount of the previous time I had stopped the engine at sea heading down the Dutch coast (see earlier blog post). I had assumed that was the worst of any fuel contamination and the lack of gunk in the prefilter seemed to suggest it was not a major problem.

The engine continued to struggle and at times it was only the large flywheel which kept the engine ticking over despite still maintaining around 250-260rpm (timed on the ever dependable Casio G-shock). We ensured a safe distance and suitable tide conditions so we would not jeopardise the ship if we did end up drifting and I shut the engine down. The removed the prefilter and emptied the brown gunk out of it and flushed through the plastic filter and then changed the main engine diesel paper filter. The diesel was turned back on and the main filter was cracked open to allow the diesel to drain through.

As far as I can tell there is no fuel drain for bleeding the system so the fuel just has to work its way through. I set the engine up for a hot start (without the plugs) and attempted to start it. After about 3 failed starts we had insufficient pressure in the start system so I pressed the electric 20 bar compressor into service to charge the main start bottle. Whilst the compressor charged I thought I might as well use the time wisely and drain the exhaust manifolds of the heavy black tar which builds up. One of the taps on the bottom of the large manifolds (about 50cm x 50cmx 30 cm deep) is a brass conical wedge just tapped into place. It normally needs a good hit with a precision percussion adjustment tool to knock it out. I gave it a tiny tap with the adjustable spanner as I raised my hand to put behind it. Yep, you guessed it. This tiny tap dislodged said brass wedge and it f$&%ed off at a rate of knots into the middle distance just over my fingertips. As this happened I obviously shouted the correct combination of swear words to open a small quantum singularity in the engine room which immediately swallowed said brass wedge and it was nowhere to be found. Please use your imagination to now summon as many swear words as possible and envision them spewing forth in quick succession from the bowels of the engine bay in Batman-esque "thwack", "doof" and "biff" speech bubbles.

I now had a problem of an open exhaust port which would not only spew foul sticky black oil residue but would also gas the entire engine room and be a fire/health and safety/life risk... Several bolts were tried, cloth wrapped with PVC tubing, but to no avail. Finally whilst engaging my inner boy scout I found a shackle bolt which seemed to nearly fit. A quick wrap with some cloth and a gentle tap home and the exhaust SNAFU was fixed. Onto the non functioning engine...

The compressor had recharged the system by this time so I continued to attempt to start it. Meanwhile the Skipper called Falmouth Coastguard to ensure that other traffic would be aware of our predicament since we were drifting closer and closer to the Traffic Separation Zone for commercial cargo ships.

After another 5-6 attempts at starting the engine (no mean feat considering this is not an electric start engine but has to be manually set, taking 3-5 minutes at best) she eventually fired and idled steadily. We let it idle for a few minutes while we decided what to do. If we pressed up to Portishead, the weather turned, we were caught in a foul tide and westerly then there were no major refuges for us and we could be in a bad position. As I tested the engine fore and aft it did not seem to be responding in its usual manner. At this stage our mind was made up and we limped back to Penzance. As I took the helm and sat ruminating our very close call I noticed we had a pod of dolphins which stayed with us for about 45 minutes until we rounded the corner into Penzance bay. They could obviously sense the stress and were a welcome sign of good luck (although somewhat late in my book). All thanks to the Penzance Harbour Master who managed to fit us into the wet dock for a few nights...

And this is where the story gets dirty. Not knowing the cause of the engine trouble we engaged the services of a local engineer. His first check was to look at the diesel from the drain, which you couldn't even see through. I was thick, brown, and smelled rotten. From that point it there was only one course of action. We had to drain the tank, open the access hatch and inspect the tank. After emptying 300 litres of red diesel, the first 20 litres of which was the consistency of just melted chocolate ice cream with chunks I knew it was not going to be pretty. With the tank empty I removed the access panel...

Inside was a disaster. The entire bottom of the tank was about 5-8mm deep in slimy, foul smelling gunk. After finding a rubber window wiper type tool I scraped as much of the offending and offensive gunk into a pile as possible and then shuffled it towards the bowl behind the right baffle. It made a disgusting slopping sound as it slid and slopped into the bowl, whereupon I drained it into a bucket in what can best be described as some form of mechanical bowel movement (with associated sound and smell).

The cause of the "bug" as it is known is water. As the tank vents due to expansion and contraction, it takes in moisture which then condenses on the walls of the cold steel. This encourages microbial and bacterial growth which grows on the walls or at the junction between the diesel and water (depending on whether the specific growth needs oxygen or not). You can kill off the bug with biocide but you still have to remove the physical remnants and by products which otherwise clog up and eventually strangle engine performance.

The major problem was that the baffles in the tank prevented the whole tank from being accessed by hand. As no local companies offered a steam cleaning or pressure cleaning service for tanks I had to boy scout the sh$t out of this one. Quite literally...

The problem was going to be getting the majority of the gunk from behind the left hand baffle. Although bestowed with the genetics of a Buccaneer flying father, my arms were not quite as long as a gorilla's, and worse, they did not have 7 joints in order to get around all the corners. A quick chat to the guys at Brandon tool hire and a fortuitous return of a piece of drain clearing equipment and I had the best solution I could muster. Pressure wash what I could get to with a lance and then feed the tube through the baffle with a special nozzle on the end.

Normally used for clearing drains it had one jet forwards and 4 aft (see, I am getting into the lingo already). The problem was it had no on/off button so I had to shout from the engine room up to the skipper to turn of the compressor when I wanted to empty the tank. It seemed to blast a lot of the crud out but I couldn't be sure. For anyone undertaking this sort of project you can purchase small waterproof endoscopes from various online retailers which would allow you to look around the corner or even to inspect a tank without draining it and removing the access panel. They have LEDs on the front so can light their way through the diesel and if it all goes brown you know you have bad fuel...

The next 4 hours were spent pressure washing the tank, wiping the slime off the parts I could reach and then draining the resultant brown water from tank into a 20 litre barrel and carrying the 200 yards to the industrial waste container. Safe to say by the end of the process and about 250-300 litres of foul stinking effluent I was utterly destroyed, covered in slimey brown gunk and stinking of diesel.

The tank is probably not going to stay. It has started to rust and degrade inside to the point where a wire brush was needed to dislodge the worst of the corrosion.

Long term I will be fitting:

A new 3-500 litre fuel tank with multiple inspection ports. At 5 to 5.5 litres an hour for the engine this would provide enough fuel for enough time to become bored with 5 knots.
Duplex Raycor or CAV296 filters so that should the engine suffer again you can shut off one of the filters and replace it while the other (fresh) filter takes over. Uninterrupted fuel supply to the engine whilst allowing servicing.
A 50 litre day tank so that for periods of inactivity the main tank can be left open and dry rather than full or semi full (inviting the bug to fester) so the engine can be run periodically.
A completely new set of diesel lines and shut of valves to both the generator and main engine.

One could make a decent living out of testing and cleaning diesel and diesel tanks. Everyone I spoke to seemed to have the same response - "Oh yeah, I've had that before"... Where there's muck there's brass, but there would have to be a lot of brass for me to consider doing that job again...