What is it about older boats that make them more susceptible to ethanol’s well-known fuel problems?
Over the past few years — since ethanol fuel has become common for boat engines — Naviguru has received literally hundreds of calls and e-mails complaining about problems that ethanol has created for their engines. The majority of these inquiries have one thing in common: They concern older engines, those made before around 2006, and a high percentage of them involve outboard engines. Naviguru spoke with Mercury Marine’s manager of engine test and planning development, and Mercury’s fuels and lubricants technical specialist — who between them have over 60 years of experience — to find out why older engines suffer more than newer ones and what owners of these engines can do to minimize the problems.
Boat engines comprise one of the largest segments of “legacy” engines in the country. Unlike cars, boats often operate for decades, which means that there are hundreds of thousands of older engines — many of which were built 20, 30, or more years ago — still churning the water. According to Mercury, these engines were engineered and built without the knowledge that they would be vulnerable to new fuels in the future. “No one knew ethanol would be a common additive to gasoline 20 or 30 years ago. We designed engines to run on straight gas,” he says. And it’s not just the engines that are affected by ethanol. Our source says that hundreds of boatbuilders who designed the engines’ fuel systems from the gas tank to the engine were also unaware of the future challenges from ethanol. And the very simplicity of older carbureted outboard engines seems to make them particularly susceptible.
The issues for older engines fit into three categories: old vulnerable components not designed for ethanol use, ethanol’s ability to dissolve deposits, and its ability to absorb enough water to separate.
In the mid-1980s, a committee made up of people from the U.S. Coast Guard, the Society of American Engineers (SAE), the American Boat and Yacht Council (ABYC), the National Fire Protection Agency (NFPA), and Underwriters Laboratories (UL) got together. Ethanol (known as gasohol back then) was being introduced for automobile use and it quickly became evident that it would find its way to boats. New standards for hoses were necessary since ethanol was known to attack rubber and plastics. The result was a standard called SAE J1527. Since 1984, all hoses approved for marine use in gas engines have had to be built to this standard and hoses marked “SAE J1527” are capable of withstanding ethanol blends. Hoses not J1527-compliant will quickly deteriorate, potentially causing dangerous leaks, and should be replaced immediately. Something else to consider: Fuel hoses don’t last forever and those from the 80s — even if they are properly marked — should be replaced. Most manufacturers advise replacing gasoline fuel hose after 10 years, and any hose that is 20 years old is way past its life; all marine-grade fuel hose has its manufacture date stamped on it.
Plastic and Aluminum Problems
In the course of our discussion, Mercury Marine’s fuel specialist shared with us that other plastic and rubber parts on older engines are susceptible to ethanol as well. These include seals and O-rings in the fuel system and carburetors. “Rubber materials tend to get hard and brittle with exposure, which can cause problems with needle valves in carburetors,” he says. Some of these rubber components can be partially dissolved with constant exposure to ethanol, and bits and pieces can be carried into the engine’s fuel system, causing clogs and misfires. Some older boats may still have plastic fuel filter bowls, which will degrade with exposure to ethanol and could leak, spilling gasoline into the bilge (old plastic fuel filter bowls should be replaced immediately with metal bowls).
One other troublesome area is aluminum carburetors. Before about 1990, carburetors were built with alloys that are much more prone to corrosion from ethanol. When ethanol contacts the older aluminum carburetor housings, corrosion can cause tiny orifices to clog, which results in hard starting and poor running, two of the most common complaints, especially from outboard owners. This is one of the most serious problems for older outboards because there is often no upgraded carburetor that can be fitted. The only effective solution is to run ethanol-free gasoline. Manufacturers now use new alloys that are far more corrosion resistant.
Non-engine-related problems on older boats involve the fuel-fill gasket, which with age and ethanol exposure can allow rainwater and spray into the fuel tank (more on that later), and fiberglass gas tanks. Not many boats have fiberglass tanks, which have been shown to leach out chemicals that can gum up intake valves and wreck engines. The leaching process also severely weakens the tanks, which in some cases has caused gasoline to leak into the bilge. The only sure cure is to replace the tank with an aluminum one.
Older aluminum carburetors tend to suffer from the corrosive effects of ethanol much more than newer ones, which are made out of more resistant alloys. Corrosion can block tiny orifices, causing hard starting and rough running.
Ethanol the Solvent
Another one of ethanol’s properties that causes headaches for older boats is its solvent ability. In Naviguru’s service experience, over the years gasoline — especially gasoline that may be more than one season old — oxidizes and creates gums and sludge that coat the inside of fuel tanks and even hoses. When gas containing ethanol is introduced, it begins to dissolve the gunk, which is carried to the fuel filter. Initially, this is more of a nuisance since simply changing the filters a few times usually solves the problem. But anything that gets past the filter, or is already downstream of the filter, can cause havoc in the carburetor. Carburetors have tiny orifices that get easily clogged, leading to hard starting, rough running, or even a complete shutdown. Simply getting the carburetor cleaned or rebuilt is often just a short-term solution; preventing the gunk from getting to the carb again is critical. A finer grade filter (10 microns) will prevent most particles from getting to the carb, though the filters may clog up more frequently as the ethanol dissolves the gunk. (Carry spares and a galvanized bucket to keep old filters prior to disposal.) Any hoses that lead from the filter to the carburetor should also be replaced since they may have deposits inside them that get washed into the carburetor by ethanol.
Ethanol Loves Water
Ethanol is hygroscopic, which means it readily absorbs water. This is good news and bad. The good news is that small amounts of water in gasoline are absorbed and simply get burned along with the fuel. The bad news is that gas with ethanol will keep absorbing water until there is so much that most of the ethanol and water will separate and sink to the bottom of the tank. This is called phase separation. The process is more common in older boats that may have had water in the bottom of the tank for years. Once ethanol is introduced, the water — along with more that may be coming through a leaking deck fitting — will be absorbed and can eventually lead to phase separation. This leaves a layer of water/ethanol on the bottom of the tank. If the fuel pickup — resting at the bottom of the tank where the mixture is — picks up a slug of water, the engine will quit. If that isn’t bad enough, there’s more: This water/ethanol mixture is quite corrosive, too, and aluminum fuel tanks are at risk of corroding from the inside if they are in contact with this stuff. Preventing water from getting into the tank is much easier than removing it so make sure the fuel fill gasket has a tight fit and keep your tank full — this limits the amount of water that can get into the tank from condensation. If you suspect you may have water in your tank, contact a company that specializes in cleaning out tanks. NAVIGURU has reported on several insurance claims for damage and injuries caused by using improper equipment (such as a wet vac) to clean out a tank — leave it to the pros. Not sure if you have water in your tank? You can buy a product called Kolor Kut that’s dabbed on the end of a stick and lowered into your fuel tank; it changes color on contact with water. One more thing to mention: Don’t plug the fuel tank vent in an attempt to keep moisture out. It’s doubtful much gets in that way and plugging the vent could lead to pressure in the tank, which could cause a spill.