A Success Story - Mark Thrulow

A Success Story - Mark Thrulow

My wife and I are living on board our Moody 49, Rum Truffle, built in 2006 as we cruise from UK to the Pacific via the Mediterranean, Atlantic and Caribbean.  Rum Truffle is fitted with a standard Separ Fuel primary filter and a secondary filtered lift pump serving a 100HP Yanmar engine and a fuel tank of 480l.  The Separ filter with a replaceable paper insert is good quality and services the gravity fed system very well.  However after much research and deliberation I decided to fit a FG1120 (FG) filter from Fuel Guard.  One year and about three thousand sea miles later – Gosport to Cyprus by way of Gibraltar so far, I know I made the correct decision.

My initial thought was to counter the fuel bug and water contamination risks by fitting a second Separ primary filter which would be fitted in parallel to the original, so that if one clogged/failed I could then swap it out and bring the alternative on line.  Whilst this had merits of same spares etc I was limiting my options.

The Fuel Guard filter being cleanable and visible seemed to be the way ahead; I noted the fineness of its micro filter and its water cleaning attributes.  Having spoken to Ian Currie and reviewing the options I built a system that would:

  • Provide a fine filter in front of my primary:  the guard element.
  • Give me emergency redundancy as I would run it in front of my Separ “in series” but fitted with a bypass loop and isolating valves:  the redundancy element.
  • Allow me to fit a purpose made polishing loop utilising the everlasting FG filter with a separate pump:  polishing.

I bought the FG kit together with the polishing kit; essentially a pump and tail fittings and all arrived in a timely fashion.  Once I had assembled the parts and set about designing the best system to serve all my requirements.  I realised that I was short of a few pieces but Ian Currie, after some discussion, arranged to provide the additional valves and tails and so I got down to work.

The tasks were to:

  • Tee in the FG in series before the Separ filter.
  • Set a bypass loop around the FG, allowing the FG to be taken off line for cleaning etc
  • Add a polishing circuit containing the new fuel pump (100lph)   

See Figure 1 at end of article for a rough diagram of the systems.

Fitting Lessons

After bravely taking on the tasks above in a cramped and awkward space I learnt several lessons about the fitting:

  • My gravity fed system did not have an isolating valve to stop the diesel flow.  I should have fitted one at outset but I only had enough valves for the job.
  • The Fuel Guard kit does not come with a valve thread sealant, I eventually realised this and stopped work to go to Halfords, they stock a fuel grade sealant ‘Granville Lock Thread’.  PTFE tape would not have worked and could have led to injection blockages!
  • It takes time to get things working, I allowed a day but as a gifted amateur it took me two days before I had things humming and tested.
  • Getting the engine purring at full capacity had me bleeding the system at all the main points including at the injectors.  This really was a pain but I derived significant experience from doing this, all in easy conditions.  Since then I have bled the system on a few occasions and to aid this I have fitted an additional clear pipe attached to my Separ filter with a valve.  At the top end of the pipe there is a funnel set high in the engine room.  This allows me to top up the system using fuel delivered down the clear pipe from a small bottle of fresh fuel.  I thus avoid having to use the lift pump manual lever which is awkwardly sited.  The same bottle is used to top up the clear flask in the FG if this is required.

So all was well in the end and a year later the FG has served me well.  I have had several lots of fuel from dubious sources during the year.


FG trapped a massive slug of bug and the filter completely blocked
  • The FG did its real job and I filtered out water and fuel bug before the engine failed and my paper Separ filter suffered.  I did this in conjunction with the addition of Marine 16 Complete Fuel Care.
  • The FG trapped a massive slug of bug and the filter completely blocked – see photo, but I put the FG on bypass, ran the engine on the original Separ whilst I cleaned the Fuel Guard and then restored the system.
  • I have polished the fuel roughly monthly when I have been in ports with shore power.

Operating Lessons

Operationally I have learnt that:

  • Although I have been polishing using the fuel pump to cycle fuel directly from the tank through the FG and back to the tank ie engine off, I realise that this is not really effective as the approach would be better if I could drain the tank during polishing.  I plan to do this with an external tank over the winter.  I also hope to fit a drain valve to the bottom of the fitted tank, correcting what I believe is Moody design oversight.
  • The FG came with an audible and visual alarm to alert users to build up of water in the FG flask.  I fitted this in the engine room so it is out of sight and hearing.  I plan to relocate this over the winter.
  • When the FG did its job having clogged with fuel bug it would have been really useful to take one filter out and then replace it with a clean one in one go.  For this I need a second filter, I am hoping Santa will be generous!


I am really glad I fitted the FG1120 and the polishing system.  Over the last year there is no doubt that it has kept me safer as I complete my extended cruise.  There are other ways of protecting the fuel but for effectiveness, simplicity, good design and value for money it would be hard to find a better product.

Figure 1  Rough drawing of the Fuel Guard systems fitted to Rum Truffle

Figure 1  Rough drawing of the Fuel Guard systems fitted to Rum Truffle 

NOTE: On Controls O = Open C = Closed