Reports began emerging this summer about a plague of black goo in fuel systems, clogging filters and stalling engines like an attack of the Blob. The mysterious malady seems to be more common in coastal waters, particularly in the Northeast, California, and Texas. Just how serious is the problem? That's still being debated. But it's being blamed on efforts to dilute the nation's gasoline supply with what amounts to cheap vodka. The culprit is ethanol - grain alcohol - which is essentially the same stuff reputed to help nascar drivers hone their trade running from revenuers back in the 1950s. In the Midwest, ethanol has been used as a gasoline additive for decades. Now it's spreading, and most gasoline sold across this country contains a touch of moonshine, bringing with it some unintended consequences. Boaters are now discovering that a fill-up at a marina, or topping off an outboard's tanks at a roadside gas station, has become something of a science experiment - and a bit of a gamble.
We've always had additives in our gasoline. They're put there by refiners to improve detergency and help starting. But in recent years the additives used have been driven by efforts to develop an effective and safe substitute for the tetraethyl lead (remember leaded gasoline?), which was an octane booster. The trouble started about 30 years ago when leaded gasoline was banned, in part because of its toxic effects, but mainly because it destroys the effectiveness of a catalytic converter. The need for a lead-free gas prompted a fast search for a more environmentally friendly octane booster. Most refiners settled on methyl tertiary-butyl ether (MTBE), a chemical that can be synthesized inexpensively from natural gas or coal. The stuff spikes octane ratings, allowing the revival of high-compression engines and turbochargers, and has a high oxygen content that promotes combustion and cleans up the exhaust.
Getting the Lead Out
But the early days of lead-free gas brought problems. Lead acts as a valve-seat cushion. Once removed, many engines needed to be refitted with hardened valve seats. MTBE, and the other minor additives with it, also attacked some rubber and plastic fuel system components-forcing engine manufacturers to do some reengineering of seals, hoses, and other small parts. Eventually, we made the change and all was going well until MTBE began showing up in groundwater in the states where it was first introduced, notably California. Preliminary studies indicated that although high doses produce a litany of side effects in laboratory rats, MTBE is relatively benign in small concentrations, particularly when compared to the rest of the gasoline leaking from underground tanks where it originates. Regardless, MTBE has a pronounced taste and odor, prompting a strong reaction from homeowners. That accelerated a shift on the part of refiners toward the more benign ethanol. Which is why this summer virtually all states were selling E10, gasoline that is 10 percent ethanol. Made primarily from fermented and distilled corn, ethanol is an even more effective octane booster than MTBE and contains about five times more oxygen. It's also considerably more expensive, and cynics quickly note that the enthusiasm for ethanol seems highest in states where corn is grown, giving agribusiness a new opportunity to make a few extra bucks. Still, the octane improvement from 10 percent of ethanol can move gasoline from 82 to 85 octane, and as an oxygenate, it's five times more effective than MTBE. So what's not to like?
Gas on the Cob
The long experience with E10 in auto engines would seem to indicate that ethanol was the answer. All of the popular gas marine engines in use today are converted from automotive blocks. And all currently produced marine engines are warranteed for use of up to a 10 percent ethanol mix. Mercury notes that its inboards and even its two-stroke outboards were made E10 compatible in 1991. For earlier models it recommends monitoring for any swelling or leaking of seals or fuel system components and replacing them. Other builders have similar policies. All's well, right? Not quite. Marine engines don't have electronic controls to monitor oxygen content in the exhaust as do cars. This "closed-loop" system is needed to make a catalytic converter work, using an oxygen sensor to tell the electronic engine control to richen or lessen the fuel mixture when it sees a change.
Most marine engines have an "open-loop" system, which lacks an oxygen-sensing capability. The computer simply meters fuel to have a predetermined air/gas ratio. Sneak some oxygen-rich ethanol into the gas and the engine gets a lean mixture without knowing it. As little as 10 percent ethanol can lean things out enough for an engine to misfire, lose power at wide open throttle, or become hard to restart while hot. Whether your engine acts this way is partly a function of its age. New EFI engines most likely have had their controls set to accommodate an ethanol mix - older ones may need a carburetor adjustment, or even larger jets.
More Goo for You
Once you get all that resolved, ethanol still has a few tricks left to make your boating life interesting. For one, it's a good solvent for the varnishes and other goop that precipitates out of gasoline; particularly the stuff that accumulates when gas sits in the tank for extended periods, such as during winter storage. Shifting to an ethanol blend before putting the boat away can free up a lot of nasty stuff that can clog fuel filters and orifices in the fuel delivery system. Okay, so you keep the gas fresh, use a good stabilizer when storing the boat, and even check the bottom of the tank for crud buildup. That's not enough. What's out of your control is when the marina shifts to an ethanol blend after using the old stuff for years. Now the solvent action works on a giant scale in its storage tanks. Until the new fuel flushes out the system, you're filling up with decades of accumulated glop. Another problem is the effect ethanol has on some fiberglass tanks. According to research done by BoatUS, certain tanks made with polyester resins up to the early 1980s have been reacting with the ethanol. The dissolved resins are being carried in solution right through the filter and into the engine, where they become a sludge deposit capable of seizing valves, bending push rods, and damaging pistons. Some tanks have been weakened, even becoming porous. However, newer tanks made with vinylester resin have not had the problem.
Ethanol has another chemical quirk that could be problematic. It has an affinity for water. The chemical bond between ethanol and water is so great it pulls water out of the air and picks up any molecules of water mixed in with the gasoline. The ethanol-water mix separates from the gasoline - much as excessive water alone does. But the ethanol-water mix can still power the engine. Or more likely, the engine will burble along as it first picks up the gas in the tank, then the ethanol-water mix. This results in a rough-running engine. The worst case is a two-stroke outboard that needs oil mixed with the gas. If the ethanol-water mix separates from the gas, it contains no oil and will quickly destroy the engine if there's enough to keep the engine running. Yet another characteristic of ethanol is its electrical conductivity, which is sufficient to cause galvanic problems and corrosion in aluminum gas tanks.