Fuel Tank Level for Winter Storage

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otter
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Joined: Wed Aug 26, 2020 10:16 am

Fuel Tank Level for Winter Storage

Postby otter » Wed Sep 15, 2021 11:11 am

Q1: is a full tank best to prevent moisture buildup over winter?

Also, on a related topic:

Q2: what method can be used to indicate then a boat's fuel tank is nearing full capacity?

I notice [on this particular boat that] when filling the boat's tank to full capacity the only way I find out the tank is full is when gasoline overflows the fuel opening on the boat. The pump hose does not automatically shut off from back pressure.

ASIDE: I have the 1998 17 Outrage II with an internal fuel tank capacity of 56-gallons. For winter storage I will be filling tank to full capacity and adding [STA-BIL] fuel additive.

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Phil T
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Location: Was Maine. Temporarily Kentucky

Re: Fuel Tank Level for Winter Storage

Postby Phil T » Wed Sep 15, 2021 11:48 am

Know that your tank has a "capacity" of 56 gallons, usable capacity is less.

Fuel gauges are fickle, each has a personality. "1/4 means X gallons, 1/2 = Y, etc. Have you determined what your X, Y and ETC?

I go by the gauge [indication, and], never by the shut-off.

The tank does not need to be full. More than 3/4-FULL is acceptable.

I presume you stabilize each gallon at each fill-up.
1992 Outrage 17
2019 E-TEC 90
Member since 2003

jimh
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Re: Fuel Tank Level for Winter Storage

Postby jimh » Wed Sep 15, 2021 12:28 pm

otter wrote:Q1: is a full tank best to prevent moisture buildup over winter?


I don't find there to be a clear preference for needing a gasoline fuel tank to be filled to FULL as the best method to prevent moisture build up over winter storage.

The salient element in this discussion is your use of the term "build-up", which suggests that during winter storage there will always be an unavoidable increase in moisture in the fuel tank. I don't really believe that premise.

I think most water in a fuel tank arrives in the fuel tank primarily by these means:
  • the water was in the fuel as it was dispensed from the retail fuel pump
  • water leaked into the fuel by leaks in seals in the fuel tank's upper surface where the water was pooling
  • water leaked into the fuel tank via the fuel filler piping and hoses due to a poor seal at the filler cap.

My usual practice for winter storage is to have the level in the fuel tank be above HALF-FULL, but not more than 3/4-FULL. The advantage of this is that on re-commissioning the boat the next Spring, I don't have to immediate buy fuel. I run last year's fuel until the tank level is at or below 1/4-FULL, then buy new fuel.

jimh
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Re: Indicator for Fuel Tank at FULL

Postby jimh » Wed Sep 15, 2021 12:29 pm

otter wrote:I notice [on this particular boat that] when filling the boat's tank to full capacity the only way I find out the tank is full is when gasoline overflows the fuel opening on the boat.


Your description is unclear to me.

Q3: does the overflow of fuel occur at the fuel filler inlet fitting?

Q4: or, does the overflow of fuel occur at the vent fitting?

If you fill the tank to the point that there is fuel remaining in the fuel filler hoses, you are inviting problems. The permeability of the hoses used in the fuel filler piping are not rated for continuous exposure to gasoline. If you leave them filled with gasoline for six months (or longer) you will likely have some permeation of the rubber hose walls.

Jloutrage
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Re: Fuel Tank Level for Winter Storage

Postby Jloutrage » Wed Sep 15, 2021 9:15 pm

I have the same 17 outrage ll. Store at 95% full for winter storage to minimize condensation. Fill to full and burn off a few gallons before storage. Add stabilizer prior to final fill and then burn off a few gallons to distribute stabilized gas through the system.

I put my ear close to the fuel fill and listen for the tank to reach full, eliminating gas from exiting the overflow. Pretty easy to tell when the tank is full.