Fuel leaks can be among the most disconcerting repairs to undergo on a boat. Worst case scenario they are notoriously hard to find and fix if situated in an inaccessible location; best case scenario they can be nerve-racking when you discover them. Gas fumes can be dangerous and although fire is rare on a boat, gas fumes increase the chances significantly. Liquid gasoline is not incredibly flammable, however, it's fumes are. If you light gasoline on fire and look closely at the flame, you'll notice it's actually the air above the liquid that is on fire.
What to do if you discover the leak out on the water
1. Do not let fumes become trapped. Explosions happen when there a high concentration of gasoline fumes in a closed space and a spark from something electrical contacts the fumes. Try to keep the bilge, head, or any other compartment that smells strongly of gasoline aired out. 2. If the smell is very strong or you see liquid gasoline in the bilge/other areas, head for the docks/shore. Even at the possible expense of disappointing your buddies or your kids, head in for the day. This is one raincheck they won't mind taking. 3. If you're leaking gasoline into the water, contact the Coast Guard and advise them. 4. If you see any gasoline or are leaking any gasoline, get the boat out of the water as soon as possible. Your favourite fishing hole will thank you.
Finding the leak
1. Note the characteristics of the leak such as:
- Is the smell stronger with full tanks?
- What activities are you performing when you smell the fumes the strongest?
- Can you isolate the smell to a particular area?
- Can you see any gasoline in the bilge?
- Do you see any gasoline outside of the boat?
- Are your gas gauges working?
2. Begin to check common locations such as:
- Hoses running to engine
- Hoses from filler cap
- Vent hoses
- Hose clamps
- Sending units
- Top of tank (water can sit on tank and corrode it over time)
3. Look for stains, dissolved foam (around fuel tank), shiny stains
4. Use compressed air:
- Get a bucket of soapy water and a rag
- Cover all possible connections, hoses, and tank with soapy water
- Blow compressed air into the tank and watch for bubbles
Note: Some marine shops may provide special fittings where you can pressure test the tank
Accessing the leak
Many boats have their fuel tanks under the deck and are built without access to the sending units nor filler hose in mind. Your best bet is to buy a deck plate, obtain boat specs and drawings from the boat builder, measure out where the sending unit and filler hose are attached, and drill a small exploratory hole. If correct, then cut out an access hole to the size of the deck plate you purchased. On any boat, you want access to the sending unit and the tank anyways. Sending unit gaskets go out over time and it's always nice to be able to check hose clamps during yearly maintenance so a fuel leak could be the perfect excuse to add those access plates to your boat.