Ethanol Becomes Suspect In Fiberglass Fuel Tanks

BoatU.S. Technical Services, through surveyors and boat owners has received a handful of complaints ranging from destroyed engines to leaking fuel tanks. Oddly, none of the owners reported clogging fuel filters. 

The reports were mostly from Long Island Sound in New York that had just switched to gasoline containing MTBE to gasoline with ethanol. 

It wasn’t long before ethanol became suspect. With thousands of boats built with fiberglass tanks since the 1960s, the potential damage, as well as the risk of explosions, was worrisome. 

Adding to the concern is that ethanol is fast replacing MRBE around the country. 

BoatU.S. contracted with Rick Strand of Impact Matrix Systems to test samples of two sections of deteriorated fuel tanks that had been cut from 1967 and 1970 model year Bertrams. Strand’s tests confirmed that the 1967 sample had an absorbed fuel content of 4.19 percent by weight, and the 1970 tank had absorbed 4.22 percent. 

Strand considers these amounts high for polyester-based composites and about the most that this type laminate could absorb.  In comparison, he says, the highest moisture content seen on badly blistered samples of laminate is only about 4 percent.

Another independent test shed even more light on the creation of damaging "black goo." Fred Hochgraf, senior scientist at the New Hampshire Materials Laboratory, analyzed damaged intake valves to determine the composition and cause of the goo.

"After taking the extract down to dryness, we obtained the infrared absorption spectrum. We found that the material is di-iso octyl phthalate." 

Gas Chromatography Mass Spectometry (GCMS) showed that gasoline having 10 percent ethanol picked up four very heavy molecules from fiberglass and two from the filler.  Hochgraf noted that a control sample with straight gasoline did not pick up these molecules. 

After evaporating a gasoline sample with 10 percent ethanol, a heavy brown sludge remained.  Infrared spectroscopy showed molecular similarities between the sludge and the material taken from under intake valves.

A dozen more reports have come in to BoatU.S.  Questions remained:  What about California and the Great Lakes?  A call to the California Energy Commission revealed one possible reason – California’s gas has only 5.6 percent ethanol. 

After a BoatU.S. press release was picked up by California publications, frustrated boaters in California and the Great Lakes began to call in reporting similar symptoms.  Because of the difference in laminate quality, some tanks may take longer to be affected while others suffer deterioration sooner.

Meanwhile, anyone with a fiberglass tank should keep a wary eye out for black goo (look under the carburetor.)  An engine with goo should not be run until it is cleaned.  Thus far, the only cure is to replace the fiberglass tanks wit aluminum or polyethylene tanks.  Or, as at least one boat owner did, take the money he would have spent on a replacement gas tank and use it as a down payment on a diesel.

Arizona already uses ethanol to boost the oxygen content in wintertime gasoline. Winter fuels are 10 percent ethanol by volume. And ethanol demand has increased in summer as well, since the state banned the use of MTBE.  The Phoenix metropolitan area, including Maricopa County and parts of Pinal and Yavapai Counties, are required to use special gasoline blends during the winter and summer to meet federal air quality standards. Tucson also uses a special blend during the winter months. The rest of Arizona, outside the metropolitan Tucson and Phoenix areas, uses conventional gasoline year round.

All gasoline that is delivered to retail stations in Maricopa County must be blended with ethanol (10 percent by volume) to help reduce carbon monoxide emissions for improved air quality. The blending of ethanol into gasoline occurs at the terminal rather than at the refinery because ethanol cannot be delivered though pipelines. Ethanol is not delivered through pipelines because it attracts and absorbs water that may be present as condensation in the pipeline and thereby contaminate the gasoline. Ethanol is also a corrosive and continued transport of ethanol within pipelines could compromise a pipeline’s physical integrity.

-Nunes developed this story from an article in the Coast Guard Auxiliary Beacon, which is published by the Coast Guard Auxiliary Association.