by Bob Adriance, published in BoatUS Magazine September 2007, reprinted in whole with permission.
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| For better or worse, a shotgun wedding took place last year between boat owners and ethanol-enhanced gasoline. Everyone wore black. Now that the honeymoon is over, it seems that at least some of the warnings of matrimonial acrimony may have been premature. |
| The key word is some. The fiasco with deteriorating fiberglass tanks (see BoatUS.com/Seaworthy) has certainly been painful for owners of many Bertrams, Hatterases, and other typically high-end boats. BoatUS Technical Services has documented over 70 reports of failures, including leaking fuel tanks and wrecked engines, from both coasts and Hawaii. In all cases, fuel tanks had to be replaced. |
| But what about the widespread reports of clogged filters that boat owners on Long Island Sound experienced when ethanol was introduced there two years ago? Why does there appear to have been fewer complaints of clogged filters this year when ethanol arrived at pumps throughout much of the rest of the country? |
| John McKnight at the National Marine Manufacturers Association (NMMA) surmised that boat owners are better prepared for ethanol than boat owners on Long Island Sound were in the spring of 2004. That's not to say that boat owners in other parts of the country haven't had plenty of problems but there is now a consensus on how best to cope. |
| Avoiding Phase Separation |
| Another, perhaps larger, test will come over the winter when boat owners prepare their boats for seasonal lay-up. One of the unfortunate properties of ethanol is its ability to attract and absorb water. Ethanol-enhanced gasoline can absorb roughly 10 times as much water as MTBE, a fuel additive now largely phased out, and still burn safely through the engine. But if ethanol becomes saturated, which can happen when it sits for long periods, the ethanol separates fro the gasoline, forming two separate solutions. This is called phase separation and it's bad news for the engine. An engine won't run on the (water-soaked) ethanol solution, which sinks to the bottom of the tank and is highly corrosive. |
| There is no quick fix. Once phase separation occurs, additives and water separators can't help; the only remedy is to have gasoline/ethanol/water pumped from the tank. |
| While all of this may sound discouraging to anyone planning to lay up their boat with ethanol in the tanks over the winter, the good news is that E-10 has been a fact of life in certain areas of the Midwest for over a decade and there have been relatively few problems. Seaworthy talked to several marina operators, surveyors and boat owners in the Chicago area who had the same reaction to ethanol: "It's no big deal." |
| No big deal? How can E-10, which attracts moisture and can fall apart, be expected to survive the winter? With any fuel that will be sitting for a long time, it is important to add stabilizer - an antioxidant - to extend the life of the fuel. What a stabilizer won't do, however, is prevent phase separation. |
| Several sources, including one prominent engine manufacturer, recommend running the tank down to almost empty and then adding stabilizer. The following spring, the tank can be refilled with fresh gasoline. Lew Gibbs, a senior engineering consultant at Chevron, worries that leaving a few gallons of gasoline might attract enough condensation to cause phase separation. If that were to happen, the highly corrosive ethanol/water mixture would settle to the bottom of the tank and would remain there even after the fresh fuel was added in the spring. |
| Gibbs said his first choice would be to completely empty the tank when the boat is laid up and then refill it the following spring with fresh gasoline. Unfortunately, completely emptying a built-in tank safely is nearly impossible. His next choice, one that's more practical, is to top off the tank to 95% full (to allow for expansion). A tank that's almost full reduces the flow of air into and out of the vent, which reduces condensation on tank walls. Any condensation that does form will be absorbed by the gasoline. (Note that the National Fire Protection Association [NFPA] also calls for tanks to be topped off to minimize explosive vapors.) |
| Gibbs said the worst choice, which was confirmed by marina owners in the Midwest, is to leave the tank half-full over the winter. Jerry Metzger, the general manager of Chicago Harbor's nine marinas, said phase separation problems typically occurred when boats had been stored over the winter with tanks that were a quarter- to half- full. The tanks breath more and attract larger amounts of moisture. Metzger says boaters in the area have learned to fill the tanks before the boat is laid up for the winter. |
| Note, however, that phase separation can occur anytime E-10 sits for a long time. On Long Island Sound, which has been using ethanol-enhanced gasoline for the past couple of seasons, Mitch Kramer of TowBoatUS Oyster Bay said they haven't had any problems with their own boats, which are used every day. Kramer says the problems now on Long Island Sound seem to be with boats that are used infrequently. Half-empty tanks that sit for long periods are more likely to attract moisture, which causes phase separation. The key: Use your boat! |
| One final not: DON'T try to plug up the vent to prevent moist air from entering the tank. Without room to expand, the additional pressure could rupture fuel system components. |
Preventing Phase Separation Over Winter Storage
DO...
Add a fuel stabilizer.
Top off the tank (to about 95% full).
Use your boat frequently during the season so
that gasoline doesn't go stale in the tank.
DON'T...
Leave the boat's tanks partially filled.
Let the boat sit idle for months over the summer.
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