Winterization of the current gas in the boat question.

Hey guys quick question, I filled the boat up with 91 octane about a month ago hoping I would use it a lot more before they shut the boat ramps down here in Colorado and the local lake shut down super early and I wasn’t able to get out there unfortunately.

My question is it’s filled 9/10ths of the way with 91 octane the pump says (can contain up to 10% ethenol) so I this gasoline considered E-10? I heard that’s super bad to let sit over winter with E-10 and additives won’t help it from attracting water and separating. What should I do? I own a fake a lake as well so I can run it out of the water Incase I need to run it with additives.

Not sure it is matters but the boat is a 2005 moomba mobius Lsv. Boat sits in a heated shop too btw.

"super bad" is a bit extreme. It is definitely "ickier" than non-ethanol fuel but it's not the end of the world. I like to put Stabil in the fuel for storage. The best is if you can add it before filling so that it can mix up fully and then run the engine for a while to get treated gas into all of the lines. But at this point, I'd probably just put some in the tank and let it sit, it will homogenize in the tank with time.

The compounding factor with ethenol fuel is oxygen. I have definitely had trouble leaving it untreated in small carbureted engines (lawn mowers, weed eaters, snowblowers, etc) as these are much more "open" to the air. I have left the boat tank untreated for the winter without any trouble: fuel injection and overall volume yield much less exposure.

Add marine Stabil and you'll be fine. Run it on the fake lake if you want for more piece of mind. This is what I have done for 13 winters.

Add some of the Stabil 360 blue to the tank, haul the boat around the block, then run it on the fake a lake for about 5 minutes to get the treated fuel into the entire fuel system. Enjoy winter and dont worry.

I use Mercury Marine QuickCare. Seems to work on E10 gas pretty well. For some reason i have never trusted Stabil since the early 2000's when i used to use the red stuff and each spring/winter i would have carb problems in my snowmobiles, law mowers etc... I use a combination of QuickCare#1 and QuickStore #3.

I always use Star Tron to treat all of the gas in my "Toys" and lawn equipment and haven't had any issues but in my boats I always try to only fill up with Ethanol Free and I still use the treatment for safe measure. If I was in your situation I would put the treatment in, run it with the fake lake, and then top the tank off full as to allow as little room for air/condensation as possible. That is what we do with our snowmobiles up in Michigan every year and we don't have any problems with them which is pretty remarkable considering they only get ridden 3 weeks a year! LOL