Interested in cleaning out diesel tanks? Like talk of filth, choking and pumping? Or perhaps you’re struggling to sleep? If so, this is the post for you!
Over the last few years I’ve had nagging doubts lurking in the deepest recesses of my mind about our Macwester Malin’s fuel system. These question marks were completely unfounded, however when you buy a used yacht, you really can’t be certain of the integrity of components until you get up close and personal with them.
Our Macwester Malin has two large fixed fuel tanks, and three or four years ago I decided to stop filling them up at the end of each season and run them down instead, so that I could open up the inspection hatches and have a look inside (see above). Part of the overhaul project included dismantling and cleaning other components such as the pipework that joins both tanks, changing both fuel filters, servicing the Jabsco raw water cooling pump, and trying to find out why our Malin’s diesel tanks occasionally leak when they’re brimmed and our yacht is healed over.
Given there was up to a 100 litres of diesel in the tanks, I bought a 12v pump capable of transferring 45 litres per minute, and 10m of hose. Unfortunately the hose wouldn’t navigate a join in the fuel-fillers, so the skipper of Joint Venture helped get the inspection hatches open and we emptied the tanks in a matter of minutes. The bottoms of both tanks were pretty filthy, but the good news was that this filth didn’t appear to be diesel bug. The filters inside the tanks were completely choked (see below), and my chum reckoned that problem would have led to engine problems within the first 24 hours of engine usage during the new season. That being the case, my unfounded nagging doubts (a.k.a. paranoia) turned out to be a good thing.
As there was still a smattering of diesel on the bottom of the tanks, I agitated the murky contents with a stiff brush and then cleaned out what I could. Then, by decreasing the hose diameter incrementally, I pumped 25 litres of clean diesel back into the tanks with a little bit of pressure, and went through the agitation process once more before pumping it all back out again. After drying, I brushed the bottom of the tanks, and finally used a vacuum cleaner to suck up any remaining loose debris.
A week later I had another session brushing the bottom of the tanks in the first instance, and then using a telescopic magnet to reach the distant corners. I was surprise by how much debris was still inside, so I kept using the magnet until the diminishing returns diminished to the point of being unrewarding.
We dismantled the filters and pipe that links both tanks and I took those home for cleaning. I considered mothballing the starboard side tank, but having looked at the options and taken advice (thanks), I decided it was better to keep them both operational on the basis that it’s arguably the best way to stop the tanks from rusting.
I reassembled the pipework that links the tanks and re-installed the clean filters inside. When it came to re-sealing the inspection hatches, I bought 100g of Hylomar Blue gasket & jointing sealant, along with two 200mm x 200mm x 3mm sheets of nitrile which made up the new gaskets.
For the record, this was the first time that I had changed the secondary fuel filter, and I soon realised that it was impossible to simply unscrew the filter (see above), as there wasn’t enough room to drop it out of the housing. I therefore had to remove the housing from the engine block to get the filter off. None of this effort qualified as additional work, as I had to remove the secondary filter and the filter housing in order to get an allen key into the lower bolt that attached the Jabsco raw water pump to the engine block any-which-way. The good news is that the secondary fuel filter was clean and contained nothing but clean fuel.
My friend from the club took the Jabsco pump away and drilled out a bolt that had been left behind when the top of the bolt sheared off. The following paragraph is a particularly boring one for my future reference, so please feel free to skip on to the next paragraph.
The raw water pump is a Jabsco 29470 2531C model. The impellers we have always used have ten blades. The Lombardini part number for the ten blade impeller is 0042002040, while the Jabsco part number is 18653-0001-P (although “–B” is the same as “–P” without the gasket). Having spoken with Jabsco, a six blade impeller is also suitable (part number 653-0001). Jabsco stated that there was no difference in performance or longevity and it was okay to use either. In the end I bought the Jabsco SK405-0001 service kit which came with a ten blade impeller (although the SK405-0001 service kit typically comes with a six blade impeller), mainly because I wanted to replace all six of the bolts, because with the benefit of hindsight, I now think the existing bolts were non-original and could explain why one of them sheared off. The cost for the kit was £50 including VAT and delivery. Did you read all the way to the end of this paragraph? …well I told you it was boring.
Our chum from Ragdoll popped over for a look inside the tanks. He was briefly over at Port Edgar, before heading back to James Watt Dock on the Clyde, where Ragdoll was waiting ahead of a trip south to Liverpool. Having had a good poke around and performed a HD video survey, he gave the tanks the thumbs up. Not perfect, but pretty solid and serviceable. I bought some replacement braided hose and set about re-working the venting system as that appeared to be an unorthodox sealed configuration that might be the cause of the diesel leak. I didn’t get too far into that project before I spotted that the tanks actually are vented overboard not sealed, as the hoses running around the engine bay are not connected. Instead there is a hidden crossover and the hoses vent over the opposite side of the hull from the corresponding tank.
Granted, overhauling the fuel system wasn’t the most exciting of pre-season maintenance projects, and combined with my crane-out finger injury, it delayed the work that I still have to do to complete the heads compartment, but we now have substantially improved the fuel system, and that should mean that we’re less likely to have fuel-related problems out on the water. It’s fair to say that as we haven’t actually had any fuel-related problems since we bought our Macwester Malin back in 2011, that doesn’t feel like much of an achievement. However another way of looking at it is that we were destined to have fuel problems in the first few weeks of the season, and following the overhaul we’ve substantially reduced the likelihood of that happening.
In a last-ditch attempt to make this post a little more exciting, the shot above shows the Cutty Sark’s rigging …taken at the weekend in Greenwich, London. The crew and I walked around her and mused about the adventures she’s seen; inevitably our thoughts drifted to the adventures that lie ahead for our Macwester Malin over the coming months.
With just two weekends left to prepare for crane-in, it’s going to be a challenge to squeeze in; getting the engine recommissioned (including bleeding the fuel system), anti-foul painting, re-installing the mooring, repairing the dinghy floor, restocking, refitting the anchor, sails and the cockpit tent.
Guess what I’ll be doing at the weekend?