Many boaters don't think of their fuel system, except when filling the tanks, but maintaining the fuel system is critical.

I can smell diesel fuel a long way off. So when I recognized the familiar scent as I was sliding through the inlet after a good day of fishing, I knew immediately something was wrong. A quick check in the engineroom confirmed my fear when I spotted the telltale sheen in the bilge water. I quickly flipped off the breakers on the bilge pumps so I would not pump water overboard, but I could not quickly find the source of the leak. The engine was running fine and boat traffic was thick, so the best I could do was get to the dock and look for the leak there.

It took about 10 minutes to find the source and it was an odd one. The return line fitting from the port engine had loosened at the tank sometime during my trip and instead of flowing into the tank, fuel dribbled out steadily. Mixed with the bilge water, it provided me with the fuel oil bouquet that got my attention. In all, maybe a quart of fuel oil seeped into the bilge and I was able to remove most of it with a few absorbing clean up pads. I was grateful that it was not a gasoline leak, but I also was concerned because the location of my return line fitting made access marginal. I then checked the starboard return line fitting by first removing several drawers from the tackle center and verified its integrity. By the end of the afternoon, I had gone over my entire fuel system for both engines and the generator and made sure every connection was clean, dry and tight.

It is easy to take fuel tanks and systems for granted, but my experience that day reminded me how important it is not to overlook the obvious. Sure, most savvy skippers know to keep the metal nozzle in contact with the fill pipe when dispensing fuel to prevent static sparks. But as I learned that day there's a lot more to fuel tanks than simply filling them.

Most permanent fuel tanks are housed deep in the bilge where rapid changes in temperatures cause a fair amount of sweating on the tank exterior and condensation inside. The fuel filter and water separator will remove the internal condensation, but the exterior of the tank relies on air moving through the bilge to keep its surfaces dry.Welded edges on metal tanks are susceptible to crevice corrosion. Threaded and welded fittings for draw and fill lines are other trouble spots. Unfortunately, a metal tank's weakest links are the undersides and outboard side, which are difficult and in some cases impossible to see. Another troublesome situation is when a metal fuel tank is encased in foam. The idea is the foam will help anchor the tank in place and insulate it from moisture. In reality, the opposite is true and over time vibration and movement cause the foam to separate from the metal. The expansion serves as a gateway for moisture to wick its way between the foam and the tank where it often is trapped. Bottom line is that if your boat is more than 10 years old and the fuel tank installation is similar to the scenario described above, you need to take a long hard look at its condition sooner rather than later.

Use a flashlight and inspect as much of the tank as you can. Be alert for signs of corrosion, usually indicated by a white powdery residue, pitting or significant discoloration. If you can feel around the tank in places where you are unable to make a visual inspection, test for signs of moisture and dry as much of the surface as you can reach with clean rags.Tanks also should have a green bonding wire attached to them to prevent stray corrosion from attacking the metal. While the green wire is usually visible from the top, be certain it is attached to a bonding strip somewhere in the bilge otherwise there is no suitable connection to complete the bond. Trace the complete route of the bond wire to be sure.

Most metal tanks commonly receive a coat of epoxy paint or similar coating before being installed into the boat. But a rough installation can cause breaks in the coating, which over time also can allow moisture to compromise its integrity. Dab on some metal primer to any bare areas you notice after wiping the surface clean with a rag moistened with acetone or similar solvent. Pay special attention to any areas where metal strapping is utilized to secure the tank in place.

By far the best metal tank installations allow thorough visual inspection of every surface and fitting. In some outboard applications, however, the tank is often buried beneath a hatch or deck section that is screwed into place. Make sure you keep a good bead of caulk in the appropriate seams to seal out water. Every few years you should dig out the old sealant and replace it with fresh caulk. The same treatment applies to each fastener used to secure the deck. Back out each screw, clean the thread and squirt fresh caulk into the void before driving the screw back into place.

Fiberglass fuel tanks are a cut above metal versions. Not only are they immune to corrosion, but a reinforced plastic cell also can be fiberglassed into the boat to add strength and rigidity to the hull. In addition, when such tanks are installed low and on centerline, it helps to preserve a constant center of gravity and maintain a steady trim or running angle. Despite its superiority, fiberglass tanks still need to be checked regularly for hose condition and the tightness of hard fitting connections.

Portable fuel tanks used on board small boats and inflatables have their own special requirements. Not long ago I was out in my Whaler and after bouncing over a large wake, my outboard started running rough. I throttled back just as the engine stalled. I quickly noticed that the fuel connection at the portable tank had worked itself loose. I pushed the connection back into place, but the spring loaded female fitting would not seat properly and a tad of gasoline leaked from the connection. It took a while before I made enough contact to provide ample fuel to the engine to keep it running. I surmised that after several seasons connecting and reconnecting the fuel hose end to the tank, the O-rings had worn out. The simple fix was a new fuel fitting, but I was glad I wasn't far from home when this malfunction occurred.

Plastic portable tanks are corrosion free and provide excellent service in a marine environment. But portable metal tanks remain popular, too, and give years of good use when maintained properly. One annoying aspect of metal tanks, however, is the bottom edge that is prone to rusting and can scratch the deck if dragged across a smooth surface. A common accessory is vinyl guard edging that grips onto the bottom rim. A trick I learned to better preserve the bottom edge is to cut the vinyl in pieces and use small sections on the front, sides and back to allow air and water to pass underneath the tank. This is especially helpful in salt water where corrosion is a never-ending battle. If you prefer to use the entire length of edging, however, just be sure to remove it from time to time and inspect the tank rim. Clean accumulated dirt and grime and keep the edge coated with paint to forestall corrosion.

The condition of a boat's fuel tank and related fuel system is critical to safety. Check fuel hoses, clamps, fittings and the tank itself on a regular basis.