Winterizing the boat, Gas tank - full, empty, treated or not?

What is the best way to leave your boiat gas tank over the winter?
Do you leave it full, treat it with seafoam or equivalent, or empty it.

I'm imagining condensation is the main culprit in the spring start-up.
Getting ready for winterizing soon, would love to know the best way to leave the tank.

Cheers,

I have always put some fuel stabilizer and filled the tank up before I put it away for the season. No issues so far come spring time.

I have also heard some different opinions on whether it should be emptied, at least half full, or completely full. Could be a preference thing.

Fill it with high test and add seafoam. Never have had any issues!

I just put stabilizer in whatever I have in the tank, this year not much, and that seems to do it

Full tank with stabilizer if it’s a big built in tank. Small 25 litre external tank disconnect it and run the motor dry , and dump whatever’s left in your truck.

I have 2, 25 litre external tanks.

Both get emptied. ONe then gets 1/4 filled with fresh gas, treated with sea foam, hooked back up to the motor, hook up the water muffs and run the motor for about 10 minutes.

After I've run it, that is when I change the oil on the 4 stroke.

Put it away for the Winter.

In the Spring, fill both tanks with fresh gas.

SDC

I fill mine as full as possible with stabilizer no issues yet

Built in: fill it and stabilize.

Carry tank: empty it or fill it and stabilize.

Regular gas is fine. High test does nothing better for boat engines anymore since it all has ethanol added.

my tank is 87L built in. I try to keep it about 3/4 full and stabilizer. I start running stabilizer in gas in September so I have put some through, the last time I go out I put in some extra. So in spring I fill it up with fresh gas and more stabilizer. I only use regular gas in boat and jeep. Quad and lawnmower get hightest and stabilizer.

Why high test in the Quad? High octane runs cooler and slows down the combustion process and increases carbon build up. The exact opposite of what the engine needs.

Why high test in the Quad? High octane runs cooler and slows down the combustion process and increases carbon build up. The exact opposite of what the engine needs.

Some ATV's are high performance or modified, so they need to run high octane fuel. (Higher combustion ratio) When I drag raced my Harley it ran on a high mixture fuel. No clue about the lawn mower, maybe it's modified.

Add the appropriate amount of stabiliser,

Fill tank,

Take for a 10 minute ride to shake up and mix the stabiliser,

Run for ten minutes to get the stabilised fuel through the carburetor.

Arnie

Thanks for the info guys,

My plan to winterize the boat is:
- fill the gas tank, add Seafoam,
- run the motor to make sure the treated gas is through-out the engine,
- shrink-wrap the boat,
- park it and wait till spring...

Cheers,

well i just assumed that the old engines like higher octane. my 50 year old car wouldn't even run on regular gas back in the 70's. so it has gotten high high test and stabilizer all its life. don't know if it helps in my small engines but they start and run every time i use them, so right or wrong I'm not going to change now. i'm old like most of my engines and i don't like change either.

You are 100% right, keep doing what you are doing. Us older guys learned from experience. Why change when what you do in life is working.