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Guide to Keeping a Clean Bilge

By The Ahoy! Crew
Published February 2, 2023

The bilge of most boats is like the dark woods in a Brothers Grimm Fairytale.  These woods may be a fine place by day when the sun is shining and all is as it should be.  Yet, after the sun sets this is a place where anything can happen and you most likely would rather not have reason to go after dark.  A place where lurkers creep.  The lurkers in the dark woods of your boat's bilge are the consequences of a discharge leak into the bilge that does not readily leave.  Rather, they lurk.  They lurk at the high water line and in corners. They clog filters, plug limber holes, and can break pumps.  If there is dirty liquid from any source in the bilge, invariably the sloshing around or build-up of debris and grime will foul the air aboard.  Lurkers can make boats stink.  Sadly, this boat stink can and does leach into all hoses, foam, and fabrics aboard.  While bilge water is certainly not for drinking under any circumstance, it may not even be suitable for pumping overboard.  Scary, isn’t it?

Fear not, there are a number of different ways to shine a light in this dark space and take control of the situation.

Way #1

One way is to open all bilge spaces, get to know what is going on, and manage the inside of them.  Are they wet or dry?  Are they clean or dirty?  If there is liquid in the bilge, what is the make up of this liquid?  Is it freshwater or seawater?  Are there contaminants that have leaked into the bilge from somewhere?  Can you trace these to their source?  Assessing and knowing the answers to these questions is imperative to the subsequent action you take.  Namely because if there is any oil or fuel in the bilge one must take particular precautions to properly manage the disposal of the waste.  Check your local laws regarding fuel and oil disposal to stay in compliance with local regulations as you clean the bilges.  

If the bilges are wet, dry them using a sponge and bucket or pump bilge water overboard.  Trace liquids and/or contaminants to their source. Troubleshoot.  Rectify.  If the bilge area has grime or build-up in it, use a biodegradable bilge cleaner to help break down and loosen the grime.  Wipe grime and cleaner up with a big boat sponge.  Follow with a thorough rinse.  Wipe clean and dry again.  Continue to open and inspect bilge areas. Ideally, they continue to stay clean and dry. 

Way #2

Another way to keep the fairytale fear factor out of the bilge is by staying ahead of maintenance issues that can make the bilge scary and gross.  Again, like fairy tales, there are usual suspects on a boat that can, will, and do make the bilge a foul place.  Know that bilgewater can be fouled primarily by fuel, oil, grease, sewage, and/or galley waste.  

Take care to maintain the boat well, eliminate and prevent any leaks from the following sources:  

  • Clamps and hoses throughout the boat should be regularly inspected, tightened or changed if in any way questionable or compromised.  
  • Regular engine inspection and maintenance should keep your engine block clean and free of grease.  
  • Routine oil and filter changes done over pans or pads keep stray drops of oil from draining into the bilge.   
  • Fuel filters, gaskets, rings, and pumps in gasoline and diesel engines regularly inspected and routinely changed will keep this high pressure system well sealed.  
  • Pans or absorbent pads left under the engine at all times are good for collecting contaminants from known and unknown issues.
  • Shower sump and check valve should be cleaned and serviced regularly to make sure everything is draining overboard properly.
  • If a boat is equipped with a marine head/holding tank system it is wise to carry a few rebuild kits.  Marine plumbing systems have hoses, gaskets, and valves that all need regular inspection.  Any compromise in the system can cause a big stink in the bilge that is best avoided.

Attending to the bilge in this manner, one will keep the bilge clean by not letting discharge leak from any system in the boat.  

Way #3:

Another way to maintain a clean bilge is to keep any mixture of grime and/or liquids that do enter the bilge moving safely and freely out of the boat.  Safety is key when considering what mariners do and do not pump overboard.  Rightly so,there are strict laws prohibiting fuel and oil from entering waterways. Take great care to know and obey these laws when keeping your bilge and surrounding water clean.

  • A high water alarm is a good piece of safety equipment as they will audibly alert you if the bilge water raises over a certain level indicating the need for immediate attention.
  • Check valves are one way valves that let liquid pass out but not in.  However, they, like anything, can fail.  Keep them functioning properly or change them.
  • Pumps should be in the lowest part of the bilges and should be unobstructed.  We keep a bilge diaper ‘uphill’ of our bilge pump and ‘downhill’ from our engine at all times just in case.
  • Bilge diapers should also be kept beneath any known leaks to prevent fuel or oil from mixing with the bilge water.
  • Some boats are equipped with filters that are in-line with bilge pumps that separate fuel and oil from bilge water that is being pumped overboard. 

Using these techniques will keep the bilges dry and water going overboard responsibly. 

Make no mistake, keeping a clean bilge is a very important part of boat ownership.  However, it is not the most glamorous part.  That’s more what big fish, diving dolphins, and magical sunsets are for.  

Ahoy! Is for the unpredictable, the uncontrollable, and the unfortunate.  Get a quote today so that whether your bilge is clean or not, you have help when you need it.


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