Originally Posted by 9D280
Are you running alc mix? If so you may need to replace brass bits in your carbs on a frequent basis - the alcohol (As well as destroying "traditional" fuel hose rubbers - check your seals are compatible too) will also create a wonderful conductivity path for a nice bit of sacrificial corrosion with the aluminium alloys of the castings... Same will go for mismatched metals on the tank.
Running 10%. Hopefully the Merc. rebuild kits have the right stuff in them.
Here is the advice from West Marine:
Ethanol and Your Boat
New gasoline additive
The gasoline in your boat’s fuel tank may have been changed in ways that could cause problems. Many states have mandated replacement of the gasoline additive MTBE, with ethanol (denatured grain alcohol). This changeover was part of the 2005 Energy Bill, which also got rid of the requirement for oxygenated gas, the main reason MTBE, a suspected carcinogen and groundwater pollutant, was added in the first place. The bill also required ethanol, made from Midwestern corn, to be gradually added to the nation's supply of gasoline. It removed protection for fuel suppliers from MTBE-related lawsuits, a big reason why ethanol is rapidly phasing in. Most marinas are required to post the ethanol content in their fuel.
This blend of gasoline with ethanol added, called E-10, contains 10% ethanol and 90% gas. The recommendations in this West Advisor are based on use of E-10, the most commonly available "ethanol" fuel. A few states also are offering E-85 (85% ethanol, 15% gasoline, mostly available in Minnesota and relatively nearby Illinois), and some domestic cars and SUVs are designated as Flexible Fuel Vehicles, and can safely fill up with E-85. At this time, unless specifically stated by the engine/vessel systems manufacturers, E-85 is not recommended for use in marine power systems. For example, Mercury approves and warranties the use of E-10 fuels, but does not approve or warranty the use of E-85. E-10 works great in most cars, which tend to be newer than the majority of pleasure boats, and get used far more regularly and more often. Boat owners and mechanics have reported problems connected with the changeover to E-10. Some of the challenges you may need to consider:
Ethanol acts as a detergent, loosening rust, debris and other gunk inside your tank and fuel lines. This crud clogs fuel filters, restricting fuel flow and leading to stalling and hard starting.
Its corrosive solvent-like characteristics also remove resins and plasticizers from some plastic and rubber materials. Most significantly, it damages the resins in fiberglass fuel tanks made prior to 1991 (used in many Bertram, Chris Craft and Hatteras boats in the 1960s and 1970s). Tanks slowly soften and begin leaking (with the associated potential for explosion from fuel in the bilge). Black sludge is created that builds up on intake valves, causing them to stick, and on fuel injectors, clogging orifices, with the potential for major engine damage, like bent pushrods. Some resins, notably vinylester, are impervious to ethanol. Most common types of epoxy and polyester resin are not ethanol-resistant.
Ethanol is hygroscopic—it absorbs water, and will mix more easily with water than with gasoline. Up to 10% of your fuel could become a water-ethanol mix, and the liquid may undergo “phase separation”, forming a top layer of pure low-octane gas and a bottom layer of water-saturated ethanol. Since the fuel pickup is located at the tank bottom, water contaminated fuel can cause your engine to run badly, or not run at all. This low-octane fuel causes problems with performance in four stroke engines, and can cause damage in two stroke outboards from lean fuel and lack of the in-fuel lubricating oil (due to the presence of the water).
Ethanol has a short six-week shelf life, and the octane begins to decrease after that time period. A minor concern in a car, this deterioration is a more substantial problem in infrequently used boats or during winter haulouts.
Dealing with ethanol-related problems
Don’t mix ethanol-enhanced fuel with the old stuff that contains MTBE. Combination of the two additives, especially when water is mixed in, may create a gel-like material that clogs carburetors (especially in outboards). Use all the old gas before refueling with E-10 if possible, or refill with the tank no more than 20% full. A clean, dry tank is best for the first fillup.
Replace fuel filters frequently during the first few tanks of ethanol fuel. If you don’t already have one, install a fuel/water separator filter, and carry replacement elements. Be prepared to change filters on the water if your engine loses rpm, sputters or hesitates. We also strongly recommend installing a spin-on fuel vacuum gauge so that you can see when the filter needs to be changed.
If your boat or engine was built before 1990, you may need to replace old hoses, O-rings, primer bulbs or other plastic or rubber parts that are not alcohol-compatible. Inspect the system more frequently for leakage or deterioration. Most fuel hoses made after 1984 and labeled with SAE J1527 are ethanol safe.
Do your best to keep water out of your fuel. Fill up with only as much gas as you will use during the next two weeks (conversely, keeping your tank full prevents water from condensing on its walls, especially if you live in an area with big daily temperature swings). When fueling, we advise using a funnel like the West Marine Fuel Filter Funnels to prevent water and particulates from entering your system. Add a gasoline fuel treatment like Star brite’s Star Tron. When winterizing, experts are divided on whether to drain the tank as empty as possible, but you should add a good fuel stabilizer such as West Marine EZ-Store/EZ-Start or Sta-Bil.
Once phase separation occurs, additives and water separators can't help. The only remedy is to have the gas and ethanol/water mixture professionally removed from the tank. With any fuel that sits in a tank for a long time, it's important to add a stabilizer (but understand that stabilizers do not prevent phase separation). A Midwest marina owner confirmed that phase separation problems typically happened when boats were stored over the winter with tanks only 1/4 to 1/2 full. In the summer, infrequently used boats with partially filled tanks are also prone to phase separation.
Never try to plug up a fuel tank vent to prevent moist air from entering a tank. Without room to expand, the additional pressure could rupture fuel system components.