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Writer's pictureTynan

Yacht Engine DIY: How to make your own marine fuel polishing system

Are you cruising in areas with questionable fuel supplies? Are you storing your boat for long periods of time or have found condensation in your fuel tanks? If so, you definitely want to consider installing a fuel polisher.


Having a fuel separation and polishing system will save you time, money and OEM engine filters, not to mention stress over potential engine damage! We have a closed fuel polishing system for each supply, designed for simplicity and ease of maintenance, which is not connected to the engines.


CONTENTS:


  • What a fuel polisher does

  • How diesel fuel polishers work

  • Benefits of a fuel polisher

  • DIY system or buy a fuel polisher kit?

  • Components of a DIY fuel polisher


What a fuel polisher does


Keeping it short, a fuel polisher is a system that removes water, debris and bacteria from your diesel fuel. The fuel is then returned to the tank, ready for clean and efficient combustion.


How does a diesel fuel polisher work?


Fuel polishers pump diesel from the tank through a system where particles are filtered out based on the micron rating of the filters in the system. Then, based on how the fuel polisher is set up, the fuel goes through a process where centrifugal force and gravity are used to separate any water that's present from the fuel. After the fuel has passed through the system it's then returned to the tank, completing the process.


Some filters like the Racor 1000FH turbine series have a water separator built into the filter assembly, so a secondary water separation filter is not necessary. This type of "all in one" Racor filter housing is the variant you want to use in your DIY fuel polisher build to save money and time, and is the one supplied with some of the most expensive fuel polisher brands.


Benefits of using a fuel polisher on a boat


There are serious benefits to using a fuel polishing system on a marine diesel engine.


  • Keeps fuel clean for extended periods of time

  • Removes water to mitigate diesel bug

  • Extends the life of engine fuel filters

  • Keeps fuel injectors clean from particles and muck from diesel bug

  • Gives confidence that the engines will not cut out from bad fuel while under load or docking.

  • Able to clean fuel on board in remote areas

  • Keeps your fuel tanks cleaner for longer


Designing your own fuel polisher VS buying premade units


When installing a fuel polisher system you can either design and install your own or buy a premade kit and install that. Here's some of the benefits of having a DIY system.


  • The components can be spread around the engine bay or installation area, all in one manufactured polishers take up considerable space in a single chunk and are often joined together with fixed length piping, electronics and manifolds.

  • Components can be placed in areas for clear and comfortable service access.

  • You can choose to use the best components available without the overhead cost of a label and some pointless pretty custom anodizing.

  • The system can be simplified to reduce unnecessary parts that can fail.

  • Potential for large cost savings when compared to similar products from brands like Keenan Filters


Components of a fuel polisher


The key components of a fuel polishing system are the pump, diesel filter and water separator. You then need to connect all of that using adaptors, fittings and fuel hose. We'll go into each of these in more detail, but to start off here's what's in our system.


Our Yanmar 4JH45 fuel polisher


Since we have a catamaran we needed two of everything, one for each side.


  • Racor 1000FH Turbine Series Fuel Filter/Water Separator, purchased for $439.99 USD per unit.

  • Marco® UP6/OIL 12V Gear Oil Pump (SKU: MARM16408012) purchased for $351.20 USD per unit.

  • Fuel hose, adaptors, fixings and fittings to suit our layout

  • Fuse, relay and wiring to power the pump and run the ON/OFF switch back to the saloon


We also added a Racor pressure gauge which screwed directly into the Racor 1000FV10. Having this gauge allows us to monitor the system without having to pull anything apart and visually inspect it.


The Racor 1000FH was recently superseded by the 1000FV. Due to a fulfillment error we were actually sent one of each, and we prefer the 1000FH because it has a simpler design. The 1000FV has additional ports which are not necessary for this application.


Diesel filter housing


When choosing a diesel filter housing you want to consider these factors.


  • Flow rate is appropriate for the amount of fuel you want to clean

  • Size of the filter housing - Should have enough clearance around it to not impede maintenance or filter changes.

  • Size of the filters - Smaller filters have a smaller surface area so can block up faster if you do pick up bad fuel

  • Micron rating of the compatible filters

  • Which fuels it is compatible with

  • Can the filter housing be used under positive or negative pressure (will fuel be sucked through or pushed through)

  • Number of ports on the filter housing

  • Can it separate water or will you need a separate part for this

  • Global availability of replacement parts and filters

  • A clear viewing bowl is preferable


Water separator


Water can contaminate fuel in many ways including through condensation, leaks and issues during the refining process. As a result, removing water from fuel is a key function of a fuel polisher.


When choosing a water separator we're of the opinion that having it incorporated into the diesel filter housing like the Racor 1000FV10 has is the best option.


If you chose to have the water separator be an independent component, here's some things to consider.


  • Size of the filter

  • Size of the housing and how it would fit in your engine bay

  • Compatibility with fuels and hardware

  • Flow rate

  • Pressure rating

  • Having a water drain tap at the lowest point is preferable.


Pump


The fuel pump you choose needs to be able to move the fuel from the tank, through the polishing system and back to the tank so having a pump with the right amount of power is essential. Too little power can fail to move fuel through the filters while too much can cause filter housings or fittings to leak or fail, sometimes catastrophically.


Some things to consider when choosing which pump you want for your system.


  • Pump size

  • Lift height, i.e. how high can it pump fuel

  • Self priming is preferred

  • The orientation can it be mounted at

  • Is AC or DC power more suitable

  • Construction material - will it rust?

  • How heavy duty, reliable and serviceable is the pump

  • Compatibility with fuels


Adaptors, hose and fittings


The fittings, adaptors and hoses you need will vary depending on various factors including the size of your engine bay and the components in your system, in particular the thread pitch and size of the inlets and outlets. Our advice is to check the specifications of your components and what new items come with before buying anything.


When choosing fuel hose here's a few things to consider.


  • Internal diameter

  • Fuel rating

  • Pressure rating

  • Choosing a multi layered hose for abrasion resistance

  • Something that won't collapse under vacuum or swell under pressure


Once I had all my components I drew out a plan and listed what thread sizes the ports on my filters and pumps were, and what sized barbed hose fitting I wanted to maintain through out the system. Then I listing which adaptors and fittings I'd need to connect the system all together. Every boat will be different, but there are some common points you want to keep in mind.


  • You want to maintain a free flowing system with no bottlenecks.

  • Ensure the operational pressure stays within the tolerance of each par

  • Using a fuel rated thread sealant for all threaded joins

  • Do not use thread tape (PTFE tape, plumbers tape) anywhere in the system as it can damage pumps and contaminate fuel

How to install a DIY polisher


How you install your fuel polisher will vary depending on things like which marine diesel motor your yacht has, how the engine bay is laid out and what parts you chose for your system.


This video explains how ours is laid out and why I chose to set it up this way. We made it to provide feedback about our experience in case it was useful to others planning to make their own DIY fuel polisher.


Note, I've now added an additional part to the breather hose which is explained in the video description.



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