Changing Fuel Water Separator: A Step-By-Step Boat Maintenance Guide

Changing the fuel water separator on your boat is a simple task that can be completed in less than 3 hours. It is recommended to change the filter annually or every 50 hours, whichever comes first. Before starting, ensure you have the right tools and supplies, including an aftermarket fuel water separator kit, fuel system thread sealer, marine-grade silicone sealant, hose clamps, and a universal wrench kit. Open hatches for ventilation, close the fuel valve, and drain the contents of the supply hose. Install the head unit vertically above the bilge water, ensuring the hoses reach the engine and tank without kinking. Drill pilot holes, inject sealant, and fasten with stainless-steel screws. Use sealant on the threads when installing the fuel filter fittings, and smear motor oil on the gaskets or O-rings. Double-clamp the hoses to the fuel filter ports, being careful not to pinch them. Finally, start the engine and check for leaks at fast idle and during a sea trial close to home.

Safety precautions when changing the fuel water separator

Changing the fuel water separator on your boat is a simple process, but it's important to take certain safety precautions to ensure the job is done efficiently and, most importantly, safely. Here are some essential safety measures to follow when changing your boat's fuel water separator:

Prepare the necessary tools and safety equipment:

Before starting, ensure you have all the required tools and safety gear within easy reach. This includes items such as gloves, safety glasses, and a mask to protect yourself from fumes. It is also recommended to have a fire extinguisher or other fire suppression equipment nearby as a precaution.

Turn off the engine and allow it to cool:

This is a crucial step to ensure your safety. Before beginning any work on the fuel water separator, make sure the engine is turned off, and give it sufficient time to cool down. Working on a hot engine can be dangerous and may also make some parts more difficult to handle.

Cut off the fuel supply:

Locate the shut-off valve on the gas tank and close it to prevent any further fuel flow. If there is no valve, you can use a hose clamp on the fuel line to achieve the same effect. This step is important to prevent fuel spillage during the separator change.

Place a container under the work area:

As some fuel spillage is likely to occur, place a suitable container under the site where you are working to catch any leaking fuel. This will help prevent the fuel from damaging the floor of your boat and reduce the risk of slipping.

Ensure proper ventilation:

Open hatches and make sure the area is well-ventilated to prevent the buildup of fumes. Working in a confined, poorly ventilated space with fuel fumes can be dangerous.

Handle fuel carefully:

Fuel is highly flammable, so exercise extreme caution when working with it. Clean up any spills immediately, and keep flames, sparks, and heat sources away from the work area.

Check for leaks before starting the engine:

Once you have installed the new fuel water separator and reconnected the fuel lines, check thoroughly for any signs of leaks before starting the engine. Inspect the fuel lines and connections for any signs of fuel escaping.

Wear appropriate clothing:

When working with fuel, avoid wearing synthetic fabrics. Opt for natural fabrics, and avoid wearing any jewellery or watches. These precautions will help reduce the risk of static electricity discharge, which could ignite fuel vapours.

By following these safety precautions, you can help ensure that changing your boat's fuel water separator is done safely and effectively, reducing the risk of accidents or injuries.

Tools and supplies needed

To change a fuel water separator on a boat, you will need the following tools and supplies:

• A fuel water separator kit from a reputable manufacturer, such as Racor, Sierra, Moeller, Mallory, or Tempo. The kit should include a filter element, a collection bowl (clear plastic for outboards, aluminum for inboards), and a mounting bracket or head unit made of aluminum or stainless steel. Some kits may also include brass or stainless-steel threaded fittings for the hose barb.
• A universal wrench kit for installing the filter and any other components.
• A fuel system's grade thread sealer and marine-grade silicone sealant for creating a tight seal and preventing leaks.
• Proper diameter hose clamps to secure the hoses to the fuel filter's ports.
• U.S. Coast Guard-approved fuel hose, in case you need to replace any old or damaged hoses.
• A scrap of plywood and epoxy glue, if you need to create a mounting plate for the fuel water separator.
• A caulking gun, if necessary, for applying the epoxy glue.
• Motor oil to smear on the gaskets or O-rings of the element and the inspection bowl.
• Rags for cleaning up any fuel spills or leaks.
• A spent windshield washer fluid container or a similar container to catch any fuel spills during the replacement process.
• A clear glass container, such as a mason jar, to collect the old fuel and inspect for water or other contaminants.

Step-by-step process for changing the separator

Step 1: Prepare the Workspace

Firstly, ensure that you have a well-ventilated workspace by opening hatches. Place a drip pan or container underneath the separator to catch any fuel spills or leaks.

Step 2: Cut Fuel Supply

Turn off the fuel supply by closing the fuel valve at the tank. Cut the supply hose at the mounting location and drain the contents. Alternatively, you can plug the line by inserting a bolt and securing it with a hose clamp.

Step 3: Install the New Fuel Water Separator

Install the new head unit vertically, positioning it above the bilge water and between the tank and engine (or primer bulb for outboards). Ensure that the hoses reach the engine and tank without kinking or making sharp turns.

Step 4: Secure the Fuel Water Separator

Drill pilot holes at the mounting point, inject sealant, and fasten the unit with self-tapping stainless steel screws. If mounting to the hull side, epoxy-glue a painted piece of plywood as a mounting plate first, then drill, seal, and screw as above.

Step 5: Install Fuel Filter Fittings

When installing the fuel filter's fittings, use thread sealant, and don't forget to smear some motor oil on the gaskets or O-rings for the element and inspection bowl.

Step 6: Attach the Hoses

Double-clamp the hoses to the fuel filter's ports, ensuring a firm connection without pinching the hoses. If extra hose is needed, use Coast Guard-approved Type A1-15 hose of the same diameter.

Step 7: Start the Engine and Check for Leaks

Once everything is securely connected, start the engine and check for leaks at a fast idle. It is recommended to sea-trial the system close to home at high RPM, keeping a close eye for any leaks.

Additional Tips:

• Some recommend pre-filling the new fuel water separator with gas before installation.
• Regularly changing your fuel water separator is important. Yamaha recommends changing it every 50 hours of use.
• When removing the old separator, consider draining its contents into a clear container to inspect for water.
• Some separators have a clear bowl or collection bowl, which can be useful for monitoring fuel quality and draining water.
• Always exercise caution when working with fuel.

How to relieve fuel pressure in the fuel line

To relieve fuel pressure in the fuel line, you can simply cut the fuel line between the bulb and the tank. There is not much pressure in the lines, so just have a wide cup below where you take the fuel line apart. Around 1 to 2 cups of fuel will come out.

Tips for filling the new filter with gas

Filling the new filter with gas is a recommended step when changing your boat's fuel water separator. Here are some tips to help you with this process:

• Before filling the new filter, make sure you have a compatible fuel type. For E-10 gas, use a 10-micron filter.
• Prepare a safe workspace by ensuring proper ventilation. Keep the work area free from sparks or open flames, and cover any nearby upholstery or flooring to prevent gas stains and spills.
• When filling the new filter, do so carefully to avoid overfilling and spills. You can use a funnel to make the process easier and reduce the risk of spills.
• After filling, wipe the gasket contact surface with a small amount of oil, such as Yamalube 2-stroke oil, to help create a seal.
• Once the new filter is filled and the gasket is prepared, screw it on tightly but be careful not to over-tighten. Hand-tightening is usually sufficient, and you can go a little further, about 3/4 to one turn more after the gasket makes contact.
• If your boat has a primer bulb on the fuel line, squeeze it after installing the new filter to build up pressure.

Frequently asked questions