Home . Articles . How-to . Boat Doctor . How do I fix a problematic fuel system?

How do I fix a problematic fuel system?

2020 January 1

Dear Boat Doctor,

I am struggling with the fuel system on my Hylas 51, which seems to have a lot of small issues that add up to a bigger annoyance. First, I don’t have enough tankage and no good way to measure capacity. I manage as best I can with a dipstick. Filters seem to clog more frequently than I think they should. Is there any way to simplify this system? 

Bob Lindberg

Salem, Massachusetts

Dear Bob,

Take solace in the fact that you are not alone. Your complaints are pretty common.

Not having enough tankage is a common complaint, and one that’s hard to fix. You’d need to give up some space to install a new tank and be careful not to upset the trim of the boat. The most common way to deal with this is simple but rather inelegant: carry fuel on deck. Every long-distance cruiser carries yellow five-gallon jerry cans on deck lashed to the rail. An important consideration with fuel jugs is a plan to transfer the fuel to the tanks. Pouring with a funnel seems like a good idea until you try it. I recommend a small hand pump or even a siphon hose.

Fuel gauges have always been trouble on boats. Mechanical gauges only work in rectangular tanks, and the air-based systems tend to fail over time. The new breed of ultrasonic sensors from Maretron (www.maretron.com) or Blue Sea Systems (www.bluesea.com) are much better. They have no moving parts, and you can calibrate them to the shape of the tank.

Filter clogging comes from dirty fuel, and fuel gets dirty when there is water in it. The longer you store your fuel, the dirtier it will get. I’d start with a biocide like FPPF Killem (www.fppf.com) this will kill what is in the tank. Be sure to follow the label directions on the biocide, which will offer different doses for maintenance and treatment. Once treated, the organisms, dirt and water need to be removed. You can use your oil change pump to pump off the bottom of the tank, pumping until you see clean fuel. If your problem is really big you may need to call in a professional fuel polisher.

Once your fuel is clean you need to take steps to keep it that way. Be selective where you buy fuel. Fuel docks can sometimes pump water along with fuel. Check the gasket on your deck fill, which should have an O-ring on the cap. If it’s missing, water can be dripping in. And of course, keep the fuel treated with a low level of biocide.