How to install a fuel filter separator in a boat

Written by chris stevenson
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How to install a fuel filter separator in a boat
A fuel filter separator is an essential part of a boat's system. (Buena Vista Images/Photodisc/Getty Images)

Protecting your boat's engine requires one of the most important components--the fuel filter separator. Marine engines need a constant supply of filtered gas free of contaminants, which include oil, water, rust and other microscopic chemicals. Fuel filters with separators have bowls that collect and settle water so it cannot pass through the combustion chamber. Fuel filters come in spin-on canister designs or drop-in types that require elements. Either system works fine for removing harmful chemicals and particles from the engine, and can be purchased in kits, minus the fuel hoses.

Skill level:

Things you need

  • Owner's manual
  • Saw knife
  • Socket set and wrench
  • End wrenches
  • Thread sealant (fuel resistant)
  • Fuel hose (desired length)
  • Screwdriver (slot)
  • Hose clamps
  • Fuel filter kit
  • Scratch awl
  • Bolts (two transom through-bolts, spacers and nuts)
  • Drill motor
  • Drill bits
  • Oil
  • Spare gas (can)

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  1. 1

    Remove the battery from the boat, using the correct socket for the cable ends and the battery bracket. Find a good location to mount the fuel filter flange bracket. For an outboard engine, the requirement will be a below-deck mounting. For the inboard or stern drive boat, you will need an above-deck mounting. Mounting to the inboard side of the transom makes the best sense for the inboard design--the same for the outboard, but under the deck plate.

  2. 2

    Keep the filter location close to the engine between the fuel pump and tank. Measure the fuel line you'll need once you have an approximate location. Make certain you have at least four or five inches of clearance under the bottom part of the fuel filter for draining purposes when ready to mount. Use a scratch awl to mark the drill holes on the transom. Fit the proper diameter bit into the drill and drill two mounting holes through the transom.

  3. 3

    Apply thread sealant on the through-bolts. Put a spacer washer on each bolt. Place the fuel filter mounting flange against the transom and push the bolts through the holes. Add two more spacers to each bolt then hand-tighten the nuts on both bolts. Use an end wrench to hold each nut still while you tighten the bolts with the correct size socket.

  4. 4

    Dab the hose fitting threads (from kit) with thread sealant. Insert the hose fittings inside the threaded holes on the fuel filter top flange and tighten them with an end wrench. Disconnect the fuel pump (discharge side) hose clamp and the carburettor inlet hose clamp. Hold a drain pan under the fuel pump hose when you pull it off. Pull the hose off the carburettor. Discard the hoses.

  5. 5

    Cut two lengths of new fuel line with a knife saw; one hose that leads from the fuel pump to the inlet side of the fuel filter, and the other hose that leads from the fuel filter outlet to the carburettor intake. Make sure you have no sharp angles in the hoses. Attach new hose clamps to each hose end and tighten both with a slot screwdriver. Secure the new hoses in any guide brackets that held the old hoses.

  6. 6

    Unscrew the fuel filter canister from the top flange if you have the screw-on type fuel filter. Remove the top flange access lid if you have the drop-in type filter model, using the proper end wrench on the bolts. Fill the new screw-on filter with gas and dab the O-ring with oil. Carefully screw the filter canister back up into the flange. For the drop-in style, fill the canister with gas and secure the lid back on by tightening the bolts with an end wrench. (This primes the fuel filter).

  7. 7

    Wipe up all traces of spilt gas on the deck or transom area. Reinstall the boat's battery, re-bolting it to its mounting bracket with the correct end wrench. Reconnect the battery cables and tighten them with an end wrench. Crank the engine over for 10 seconds then stop. Repeat this procedure until the fuel reaches the carburettor and the engine starts.

Tips and warnings

  • No smoking or open flames around a fuel filter installantion.

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