What is Ethanol and Why Is It Bad for Outboards?
Ethanol has been added to most of today’s fuel supply as an oxygenate to help reduce emissions. It’s also used to extend domestic fuel supplies.
Ethanol is alcohol, and alcohol is “hygroscopic,” which means it attracts water molecules. Since nearly all outboard fuel tanks are vented to the atmosphere, water can (and will) collect in your fuel.
When the concentration of water molecules in your fuel tank reaches just 1⁄2 of 1%, the water molecules will bond with the alcohol and sink to the bottom, where your fuel pick up is. Depending on the amount of water ingested into your outboard, this can result in everything from running problems to catastrophic damage.
Ethanol, being alcohol, is also a powerful solvent that can loosen debris in your fuel tank and all the tanks and lines it was in before it got to you. Once in your outboard, this debris can cause everything from running issues to a no-start, no-run condition.
Install a 10-Micron Fuel/Water Separating Filter
Proactively install this filter in the outboard fuel line between your fuel tank and your outboard. It filters the gas and allows any water (which is heavier than gas) to safely sink to the bottom of the filter and out of the fuel. Yamaha’s spin-on 10-micron filter traps impurities down to 10 microns in size (1/20th of the diameter of a human hair) to keep your fuel clean, and it has an extra-large water-retention area. And since it’s a spin-on, it’s very easy to replace.
Tip: Carefully filling a new replacement filter about 3⁄4 full with fresh, stabilized fuel before installation will make priming the fuel system afterward much quicker and easier.
Tip: Apply a thin film of clean engine oil to the fuel filter gasket before installing the new fuel filter. That will make it much easier to remove when it’s time.
10-micron filters should be replaced every 50 hours of engine operation. Keeping this filter clean and fresh will help protect the other fuel filters on the engine and extend their service life. And always carry a spare on board, just in case you get a load of bad gas and the filter gets overwhelmed.
Tip: Do not simply remove and dump the fuel and re-install the filter, as captured debris and water could enter the “clean” side of the filter and be released into your fuel system.