Five places to check for trouble in your boat’s fuel system.

- —John Tiger

Fuel leaks in any boat can be disastrous, especially those hulls that have enclosed bilges, where fuel can pool unchecked and vapors explode ferociousl­y if a spark is ignited.

It’s more important than ever to keep a close watch on your boat’s fuel system. With the current use of ethanol-blend fuels that can cause damage and deteriorat­ion to fuel-system components, and continued pressure from the federal government to increase ethanol content from 10 percent to 15 percent, maintainin­g and inspecting your fuel lines is imperative. Here we review where fuel leaks commonly occur, and where to look for clues that a leak has developed or will develop. Check your tank carefully for leaks, cracks and loose mounting. Vibration and wave pounding, combined with age and neglect, can do a number on your fuel tank. Unless it’s leaking fuel into the bilge, you might not even notice it. Tanks with all mounting tabs broken or cracked are not uncommon; sometimes, the only thing keeping the tank in place is the weight of the

fuel and the tank-hose connection­s. 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.

Many boats with underdeck tanks use

an anti-siphon valve. These reside in the outlet fitting from the tank to the engine—usually threaded right into the fitting at the top of the tank—with a hose nipple on the other end, where the fuel line is installed. The anti-siphon feature (a simple balland-spring affair inside the fuel nipple) 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 (with your insurance company as well) if you experience a fuel-related boat fire due to fuel in the bilge.

Instead, replace it with a quality anti-siphon valve, available at local marine dealers. Hint: High-quality ones cost three times as much as cheap ones, and are usually made in the USA. PRIMER BULB Many outboards use primer

bulbs. These are prone to leaks as they age, weather, or become crimped and kinked. They can also be damaged by ethanol-blend fuels. Primer bulbs 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. Primer bulbs also have specifical­ly sized fittings, just like fuel filters. Use the correct size primer bulb for your fuel line and the correct size clamps to avoid leaks.


While worm-gear hose clamps, plastic tie wraps or plastic “snapper” ratcheting-type hose clamps are OK for low-pressure fuel hoses, they are not to be used on high-pressure fuel hoses. Factorytyp­e Oetiker seamless clamps are the only way to go in high-pressure applicatio­ns—and should really be the clamp of choice on all fuel lines. A special pliers tool is needed to install these clamps, and they are specially sized for each hose size’s outer diameter (OD). Use new clamps if the old ones won’t hold, or are corroded or falling apart. Hose clamps are cheap compared to a damaged engine. Be careful about using cheap hose clamps. They typically rust and fall apart quickly.

Check fuel lines from the tank to filters, then to the vent and engine(s). Be wary of a fuel line that is left exposed to the weather because it will deteriorat­e, crack and craze. Fuel lines older than three years should be replaced with federal Environmen­tal Protection Agencycomp­liant and US Coast Guard-approved hoses and new clamps. The interior linings of older fuel hoses are susceptibl­e to deteriorat­ion from ethanol and can disintegra­te from within, causing clogging, poor running and even engine failure.

The newer fuel hoses solve this problem with a tough inner liner, visible by looking into the end hose. This makes the hose less flexible and tougher to push onto a fitting. Expect to pay about twice what the older hose cost.

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