With todays fuel it is more important than ever before to be aware of the issues that arise in the marine engines. With todays modern engines the issues from the present are different than the engines from the past. With the computer controlled engines ignition problems are becoming less of a problem compared to fuel.
With the alcohol in todays fuel, water is literally pulled from the air and into the fuel. For a test, an open clear container such as a jar with an inch or two of gas poured into it can be left on a bench for a few hours on a humid day. You will be surprised to see the fuel getting cloudy or on real humid days a seperation of fuel and water. Now think about fuel tanks in boats and the condensation issues that can happen on warm humid days and the cooler area of the bilge where the fuel tank is.
Also there are the problems with plastic fuel tanks, fuel lines, primer bulbs and rubber fuel components that the alchohol likes to destroy. This leads to more expensive fuel systems that have to be EPA compliant. The portable plastic fuel tanks seem to always have venting problems, either not venting at all or every time it rains you get water in your fuel.