Avoiding Pains in the Gas

It makes sense to get your boat's engines tuned up before starting the season. But even a perfectly adjusted power plant can't do its job if you feed it bad fuel. And chances are that if your boat has been sitting idle for more than a couple of months, you need to pay attention to what's in the tank.

For years, conventional wisdom has dictated that fuel tanks be filled before storage, thus reducing the amount of trapped air in the tanks that could cause water condensations. This is still the case for diesel-powered boats, but an increasing number of experts now feel that tanks holding gasoline/ethanol blends are better left empty during the off-season. The reason: Even ethanol blends that are properly treated with stabilizers will eventually absorb some amount of water. Worst case: That water will cause phases separation, but even if it remains in suspension, it will result in a leaner fuel mixture that isn't good for the engine.

If you did leave your gas-powered boat's fuel near empty, you can start the season by simply adding quality fuel, and perhaps consider an additive that has an approved detergent that will clean out residual buildup in the lines and fuel injectors. If the tank is half full, you may be able to doctor the mix by topping off with a higher-octane blend and adding a fuel stabilizer.

A full tank of fuel can represent a fairly substantial investment, but if it's been sitting all winter ? especially if it wasn't properly treated with a stabilizing product ? it may become a liability that could create engine damage. If in doubt, it's best to test. Simple fuel test kits such as those from Quik-Check can be had for around $25. Depending on what the results show, you may be able to salvage the fuel through additives or filtration, but gasoline cannot be "polished" in the same way as diesel fuels, so your worst case may be enlisting a professional service to dispose of that tank load. It may seem like a wasteful process, but if there is real doubt as to the quality of the fuel, disposal might be a whole lot cheaper than an engine rebuild.