I'm going to put up my pontoon boat and 2 jet skis the end of this month till next spring. I have put in Stabil fuel on the existing tank of gas. Question, is it better to fill the tanks full of fuel or does it not make any difference when storing.

I would not fill tanks ,Stabil good let motor down don't leave tilted up that will let water drain Jet skis people crank up and just blow water out.

You're in Houston and putting your toys away in September for 8 months?

I'm in KC and never put mine away.

I only fill the tank if I'm forced to use ethanol gas. More air in the tank, more ability to absorb water. I also trickle charge my batteries during the winter months and run the livewell aerator pump about 15 seconds to blow out any water in the hoses. Fuel/water separator gets drained as well.

I’ve never done anything fancy to winterize a boat with an outboard. I would change the lower until oil and do an oil change (if 4 stroke) before I put it up. Put the motor down so it doesn’t freeze the housing, dump some seafoam or other fuel stabilizer/treatment in the tank, and put a battery maintainer on there. Can’t speak for the jet skis but this is about the extent of what I do in the winter. To be fair I use it in the winter too.

We always double treat the last tank of gas and run it until the gas gauge shows empty... Pull it do the yearly fuel filter, oil change, lower unit oil change and park it in the unheated garage here in E. Tennessee... Been doing the pontoon this way for the last 12 years and have never had a problem... Dan