As a gasoline retailer, the biggest problem in my opinion is that ethanol is a great solvent and really cleans out the gas station storage tanks. You'd be amazed how much varnish has collected on tank walls over the years. It will now be cleaned of and pumped into your car and boat. We were advised to switch to 10 micron filters on our pumps, but they plugged up really quickly as the ethanol cleaned varnish off of the tank walls. Some stations chose to go back to 30 micron and let the motorist deal with the junk from the tanks. In most areas, plus grade is the lowest volume product, thus it has more varnish buildup on tank walls and should be avoided. Regular moves pretty fast, so not as much varnish built up. Marinas don't move as much gas as gas stations and I doubt that they spent the money to get tanks cleaned before the ethanol was dumped in.
Water is a big time problem. If your supplier has significant water in the bottom of his tank (not unusual), it just sat there and behaved itself before ethanol. Ethanol loves water. Here's the deal:
The storage tank pickup pipe goes down to about 6 inches from the bottom of the tank. Let's say your dealer has three inches of water in the bottom of his tank. Add a load of ethanol gas. The ethanol mixes with the water and, if the proportions are right, all of the ethanol will be drawn to the bottom of the tank, forming what is called an "ethanol bottom." This ethanol/water mix might end up being 7-8 inches deep or more, so what would be sucked up through the pump is a mixture of water, alcohol and sludge that looks like iced tea. Happened to a station here in VA and about 40 cars stopped running within a few hundred yards of the station. Ethanol is blended at the delivery terminal and it's a learning process, so expect to get gas that is not properly blended and doesn't have the correct octane. We got a load of premium that was actually about 86 octane vice the required 93.
The moral of this story is avoid gassing up in the first few weeks of the transition. Ask your marina if they had their tanks certified for ethanol. It was a requirement here, but there was no enforcement and the ethanol-laced gas was delivered whether you were ready or not.
Use good filters and change them frequently for a couple of months. Every opportunity you get, lobby to stop using ethanol and go back to good old MTBE.
