ArticleBoatingService Repair


With the introduction of E-10 gasoline, and the threat of increasing concentrations, a functional fuel filter is an absolute must-have for any outboard powered fishing boat. But despite aftermarket canister-type fuel filters, your outboard powered craft might have a few others that you didn’t even know were onboard.


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Suzuki’s advanced DF250 features multiple onboard fuel filters. Photo: Captain John N. Raguso

While it has been discussed in great lengths, E-10 fuel in the marine environment brings a few pluses and many minuses to the mix. While using locally grown and refined ethanol somewhat limits our dependence on foreign oil, it also creates some hefty challenges. One such issue is the fact that alcohol-laced gasoline cleans out all of the gunk in your gas tank and fuel lines and transports it directly to your engine. Here it can cause a world of hurt by clogging up the flow, which will in turn starve engines for fuel, causing premature overheating and possible powerhead failure. Yet another problem with E-10 fuels is their tendency to experience phase separation when moisture is introduced into the fuel supply, resulting in ethyl alcohol settling to the bottom of your tank where your pickup feeds are located.

When it comes to smooth operation proper fuel flow and filtration are absolutely essential.

Adding an in-line fuel filter between your boat’s fuel tank and outboard engine(s) should help minimize these problems. To get the inside scoop I headed down to the Fort Lauderdale International Boat Show to connect with some outboard engine manufacturers and get their recommendations on what type of filters you should use to avoid these problems, along with the recommended replacement intervals.

My first stop was at the Yamaha booth, where two of their technical engineers spent an hour with me going over onboard gasoline fuel filters. The Yamaha techies recommended that every boat that uses an outboard motor and runs E-10 fuel should have a primary in-line fuel filter between the tank and the fuel feed. To address this need, Yamaha offers 10-micron fuel filters. Installing one is a 15 to 20-minute project, as long as you have the right tools and connection hardware. Start by securely thru-bolting the fuel filter canister frame in a convenient and accessible spot. Next, take the supply line from your boat’s fuel tank and snap it onto a 3/8-inch bronze barb that you have screwed into the input side of the fuel filter frame. Connect another fuel line to the engine from the output side of the filter setup via a second 3/8-inch bronze barb and then attach stainless steel hose clamps for each connection. Spin-on a new fuel filter canister and you are good to go.

Racor’s 320R-RAC-01 is a general purpose 60 GPH flow unit that employs a 10-micron spin-on canister and a clear plastic contaminant collection bowl with a handy drain plug at the bottom. Suzuki uses a private label aftermarket, in-line, spin-on, canister type unit for their primary fuel filter. The factory reps that I spoke with at Evinrude and Mercury confirmed their standard in-line fuel filters are also aftermarket types that are private labeled for them and manufactured by others. The Racor fuel filters are reasonably priced with complete mounting packages (frame, filter and bowl) usually under $100, aftermarket replacement packages (filter element and bowl) under $45 and replacement filter elements under $20.

Replacement Intervals
The Yamaha techs recommended changing out their 10-micron fuel filter canisters after every 50-hours of use. The Racor reps mentioned that their primary canister fuel filter should be changed at least once a season, or as need be if you experience a batch of contaminated gasoline. What’s cool about these filters is that you can typically see problems before they occur, just by looking through the clear contaminant collection bowl mounted at the bottom of the spin-on canister. Draining the contents will confirm any fuel contamination suspicions and enable you to take proactive measures BEFORE you develop a potential problem.

David Greenwood, the Product Planning Manager for Suzuki shared some specifics from his master service manual for changing various secondary onboard fuel filters. Looking at the Suzuki DF250 V-6 outboard as an example, there are a trio of fuel filters, all of which warrant operator attention. The first of these is the low-pressure fuel filter which is located in a small clear plastic bowl positioned just aft of where the boat’s fuel line enters the engine. This needs to be replaced every 400-hours or two-years, whichever comes first. The second unit, a high-pressure fuel pump filter, needs to be changed every 1,000-hours. The third onboard filter is a high-pressure unit located inside the vapor separator and also needs to replaced every 1,000-hours.

One way you know that you’re having some sort of fuel filter related problem is when your outboard begins to surge and/or experiences a loss of power at wide open throttle. The bottom line is that you need to be comfortable checking and replacing both your onboard and in-line fuel filters. If you have any reservations refer to your engine manual or let a professional mechanic handle it. When it comes to smooth operation proper fuel flow and filtration are absolutely essential.