For 20 seasons of boating in Minnesota I have not had an issue with ethanol. The boat gets used most weekends during the summer and is in storage for almost 6 months in the winter. I use Sta-bil in the fall, and just put fuel in it otherwise. I've used it in a 5.0 Ford EFI then a 5.7 GM EFI since 1995. I found that the 5.0 Ford was actually more of an issue because it required 89 octane.
Ric and others have mentioned Volvo having "paint" coming off in the fuel injection system. I've never experienced this or heard of it in boats, but I have personally experienced a similar situation on three occasions in the 99 Silverado pickup with a 5.3 that I used to have. At approximately 80,000 miles I noticed a rough idle and check engine light one morning. One cylinder was not firing well and was throwing an error code. I mentioned it at work that day and several fellow mechanics told me that it was the fuel affecting the interior of the 2 plastic fuel injection rails that deliver fuel to each injector. A tiny piece of plastic would flake off the inside surface of the rail and partially clog and affect the injector operation. Their recommendation was to buy a "more expensive" can of fuel injector cleaner, dump it in the tank, and run the engine for at least 20 minutes, then park it for the night. I experienced this three times over the course of less than a year. The next morning it ran perfectly each time. The truck ran perfectly after that for the next 90,000 miles while I owned it. According to my co-workers this was not a GM issue alone. Ford and Dodge engines were affected also.
Just to clarify, I'm not one to add much of any thing to fuel through the year, but if a $5 to $12 can of "snake oil" does any one any good by avoiding a repair bill, maybe they can use that money for more boat gas.
Hope this helps someone.
don't think it will cause any issues.