Here’s a fresh example of the damage ethanol-blend fuel could cause on your boat. I first saw this image of a section of outboard fuel line destroyed from the inside-out in a “webinar” presentation hosted a few weeks ago by ValvTect, the fuel-additive manufacturer. ValvTect president Jerry Nessenson used the image to talk about the effect of phase separation (when water present in the fuel causes both water and ethanol to separate from the fuel mixture) occurring within fuel lines.

 Ethanol apparently caused the inner, urethane layer of this fuel line harden and deteriorate.

Ethanol apparently caused the inner, urethane layer of this fuel line harden and deteriorate.

A little searching the web led me to the origin of this photo: Internet Lures, where site co-owner Danny Yang posted images and some video of a section of line he says came off of his 2004 Boston Whaler. Yang says this is the OEM fuel line rigged to the boat’s Mercury 225 FourStroke. He removed it after finding chunks of a hard substance clogging the boat’s fuel filter. Yang dissected the fuel line, and discovered the inner section of the line was hard as a rock and breaking up.

This is in no way an indictment of the quality of Mercury fuel lines. This line was just not intended to handle a high concentration of ethanol, which according to Nessenson can reach 60 to 70 percent when phase separation occurs. I did check with Merc, and learned that its ubiquitous silver fuel line has a urethane core and a durable PVC outer layer. So in this case, it was that urethane portion that broke up.

Since Yang’s Whaler was built, fuel lines have changed significantly to meet new EPA regs (it can no longer be permeable to fuel vapor), and it’s implied that the new line is also more ethanol-tolerant. But a Merc spokesman reminded me that fuel lines lead a rough life, often exposed to heat and UV, crimped and bent – “Fuel hose gets old fast,” is what he said. So, if you are finding hard particles or “brown sugar” in your fuel filter, check your fuel line. And if your line is getting old and you have to use ethanol-blended fuel, it might be smart to upgrade to the latest-greatest hose, which is supposed to handle up to 85 percent ethanol. Look for “ISO 8649” to be printed on the fuel line.