Marine News from the Great Lakes

DONíT BE FUELISH: Fuel Systems Check & Tune-up

Published: Wednesday, May 22, 2019
By: John Tiger

No matter the climate or your boating location, paying attention to your boat’s fuel system can pay off big – especially if you consider that a faulty fuel system can leave you stranded offshore!

Continued pressure from the federal government to increase the amount of alcohol in fuels has brought serious concerns and changes to the marine industry and the way fuel systems are manufactured, rigged, and maintained.

E10 fuel (fuel extended with up to 10% alcohol) has been difficult to adapt to, but the marine industry has made the necessary changes to parts such as gaskets, carburetor repair kits, fuel lines, pumps, filters, and injectors to combat the ravaging effects of so much alcohol in the fuel.

Let’s take a look at how to combat the effects of alcohol-laced fuels, as well as general maintenance and good practice.


The engine can’t run if it can’t get fuel. If your fuel lines are older than three years, they should be replaced with new EPA-compliant hoses and new clamps. The innards of older fuel hoses – and even new ones, especially new ones that are cheap and sold at discount stores – are highly susceptible to alcohol deterioration, and can literally disintegrate and cause clogging, poor running, and even engine failure. EPA-mandated (clearly labeled) fuel line solves this problem by using a very tough inner liner; it’s visible by looking into the end of the open fuel hose. It does make the hose somewhat less flexible; it’s tougher, for example, to push the hose onto a fitting. The new hose is also quite a bit more expensive. Take care when routing the lines; tight curves will generate kinks and flow stoppages.


If your rig doesn’t have a water-separating fuel filter, now’s a good time to add one. Typical marina-brand units work well to filter out water, dirt, and other contaminants. Placement in the fuel line should be between the tank outlet and the engine inlet.


Many outboards use primer bulbs; if your rig has one, these can be damaged by alcohol extended fuels too. These have check valves inside that can fail and leave you stranded out on the water. If it feels squishy, and the engine can “suck” the bulb flat, it’s toast – replace it. Buy an original equipment one; the aftermarket ones just do not work as well.


The clamps that keep the fuel lines tight are critical, and warrant checking. They prevent fuel leaks and, just as important, prevent air leaks. Air leaks can starve an engine for fuel. The result is a ruined engine. Use new clamps if the old ones won’t hold, are corroded, or are falling apart.


Finally, check the tank carefully for leaks, cracks, and loose mounting. Vibration and wave pounding can do a number on your fuel tank, and unless it’s leaking fuel into the bilge, you might not even notice it. If yours is cracked, broken, or corroded, replace it. While a new tank can be expensive, a boat fire is surely worse. When remounting your tank, be sure it’s not sitting directly on the boat floor; suspend it slightly above, or use a rubber mounting cushion pad underneath. If possible, create an access hole in the floor so that you can use through-bolts, nuts, and large fender washers to mount the tank instead of wood screws.

One last word, about anti-siphon valves. These reside in the outlet fitting from the tank to the engine, with a hose nipple on the other end where the fuel line is installed. The anti-siphon feature is to keep fuel from flowing into the bilge if a failure occurs in the fuel line. Some cheaper valves can cause fuel restrictions to the engine; if you experience this, don’t be tempted to simply remove the check valve from inside the anti-siphon fitting. It’s against the law and could get you in a heap of trouble if you experience a fuel related boat fire due to fuel in the bilge. Replace it with a quality anti-siphon valve, available at local marine dealers. Hint: the high quality ones cost three times as much as the cheap ones, and are usually made in the USA.


This article first appeared in the Launch Issue (May/Jun) 2019 of Great Lakes Scuttlebutt magazine.

tags: Do It Yourself (DIY), Service & Repair

Sept. 2019

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