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Should I use Ethanol or Ethanol-free gas in my Outboard Motor?

Bad fuel is one of the most prevalent outboard boat problems that we repair in Charleston SC. This is a problem not just here in Charleston but everywhere and it has a lot less to do with the quality of gas that you are buying and more to do with the gas that sits in your gas tank over time. This of course brings us to the highly debated topic: should you use a premium gas which contains 10% or less of ethanol or use ethanol-free gas in your outboard motor? Here's the short and skinny from both sides of the aisle and we’ll give you what you really need to know.


Over time, some elements from ethanol gas can produce a gummy film in your fuel system that stops it from operating properly. The key element is time...and ethanol. Therefore, it is always safer, while more expensive and more inconvenient to run ethanol-free gas.


Here is our take, you cannot go wrong with running ethanol-free gas but you can go wrong with running premium gas which contains ethanol. But, let’s get back to that key element of time. If you are the once a month weekend boater then yes, you should use ethanol-free gas. However, if you are the hardcore fisherman who is on the water every other day and you know you are going to burn through the gas in your tank in less than 48 hours, then it is okay to use your manufacturer's recommended fuel type and rating which is generally 89 test gasoline.


Regardless of whether you use a premium gas which contains ethanol or ethanol-free gas, it is not a good idea to have that fuel sit in your tank for an extended amount of time. When the gas sits in your tank over time it causes moisture to build in your fuel system which can cause damage to your outboard motor. If this is you and you know that you have old fuel sitting in your tank, it is better to syphon out the old fuel than to run it through your motor. Another critical element is one which occurs around the 30 day benchmark is what’s known as phase separation. This is when the ethanol can no longer suspend the amount of water it has absorbed from the atmosphere which causes the ethanol and water to separate from the gas, falling to the bottom of the tank which leaves a fuel that is not suitable for use due to the lower octane which can cause the detonation of a piston or to be more direct cause “the engine to blow up”.


So how do you prevent fuel issues with your outboard motor? First, if possible buy ethanol-free gas or use an additive in your gas if you purchased a premium gas containing ethanol. Second, do not let the gas sit in your motor for more than two weeks. If you're done boating for the year we suggest you winterize your motor to prevent these issues. Lastly, replace your fuel/water separator every 100 hours. We do this with our advanced outboard maintenance package and inspect to see if there is any water in your fuel so you can address it quickly before an issue arises at an inopportune time keeping you from enjoying your time on the water and paying for costly repairs. Total Boat Repair in Charleston, SC is happy to help you with any of these concerns as we are just one call away.


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