An Object Lesson In Keeping Diesel Clean

By Rich

It’s a terrible joke but I’ll make it again: marine diesel engines always fail at the worst time. From an engineering standpoint, this is a bad joke because there is a perfectly good reason why engines choose rough weather to fail: big seas stir up the asphaltenes or blobs of microbial growth, which then get sucked up into lines and filters. Many boat owners like to blame old, dirty fuel tanks or having “gotten bad fuel” at their last fill up, but the reality is that keeping fuel clean requires constant vigilance even on new boats. The ship’s log our our Hylas 54, Rover, show that she was experiencing engine failures due to clogged fuel filters when she was only a year old. Below is a great a video from Distant Shores TV showing they had the exact same experience on their one year old boat – and, as always, the engine failure occurred in an choppy inlet, which is when they always do. If you watch the video all the way through you will see that a terrible design flaw in Southerly’s fuel plumbing directly contributed their failure too.

How To Prevent Incidents Like This

Engine failures in inlets can be extremely dangerous, especially narrow, shoaled inlets. When we bought Rover the first thing we did before even leaving Charleston was to polish all of the fuel using the Hylas’ on-board fuel polishing system. See this article for what we found – and this was after a professional fuel polish a year before we bought her.  As soon as we got to Annapolis we manually cleaned all four fuel tanks because even after the polishing, our generator failed when a blob of asphaltene got sucked into the lift pump and killed it. See this article and this article for what the tanks looked looked like inside before and after cleaning. Any one of the blobs of asphaltene shown in the photos would have caused the failure shown in the Distant Shores video above.

With our tanks now clean, we are on a 30-day rotation of polishing all of the fuel on board. Between ocean passages, we keep only the 49 gallon starboard aft tank full, and the other tanks 100% empty. We circulate the 49 gallons through all four tanks in sequence every 30 days to prevent the residual fuel in the “empty” three tanks from going bad. When we see asphaltene in the bottom of tank we break it up with a wooden dowel and direct it to the fuel pickup so it can be sucked into our 10-micron polishing filter.  Hopefully this routine will keep our engine running in virtually any sea state, but if it fails us we will revise as necessary!


1 thought on “An Object Lesson In Keeping Diesel Clean

  1. Just watched the video. Now your remarks about the banjo fittings become very clear! More importantly, this proves the importance of maintaining fuel cleanliness and (oh yes!) the concept of restoring engine service BEFORE knowingly venturing into rough conditions!

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