WINTERIZING: Full fuel tank vs Empty fuel tank

[Patrick_L]

What’s better in your opinion ?
Upper Midwest

 

[Scott Danforth]

Empty tank, then tape vent shut

 

[muc]

Minnesota here.
Empty is best, but to get a built in boat fuel tank empty. You have to pull the sending unit and pump it out. If you just use the fuel line, you will leave about 1" of fuel in the tank --- not so good.
Never full, when it warms up you will have fuel everywhere. 3/4 to 7/8.
I'm against plugging the vent. One year the big boat show in Minneapolis required us to tape the vents, wasn't pretty. Boat fuel systems aren't designed to have much pressure or vacuum. Temp cycles are hard enough on them, no need to add more stress.

More important then tank level is quality stabilizer and if you have electric fuel pump or EFI ----- storage mix is real important to protect the pumps and injectors.

 

[alldodge]

My opinion from KY
Leave it where ever it is when last used. Use E0 fuel, no stabil, all good come next year. Found later where @tpenfield did a test and found no difference

 

[dingbat]

My opinion from KY
Leave it where ever it is when last used. Use E0 fuel, no stabil, all good come next year. Found later where @tpenfield did a test and found no difference

Maryland……agree…..E10 makes no difference either unless the boat was built prior to 1986 and still running OEM original (now 36 yro) gaskets and hoses.

 

[JASinIL2006]

I honestly don't think it matters. For the last 10 years or so, I've left whatever fuel (E10) was in the tank after my last outing. I almost always add Marine StaBil (although I'm not entirely sure it really makes much of a difference, but better safe than sorry!) and usually the tank is 1/3 to 2/3 full.

I've never had a problem with any sort of moisture or condensation, my water-separating fuel filter never has any water in it, and the boat has always run fine.

We also store gas similarly at our cabin in Ontario and there has never been a problem with it, either.

Unless I'm storing equipment for more than 6 months, I don't worry about it.

 

[nola mike]

Merc recommended tank full...

 

[airshot]

A lot deoends on the material the fuel tank is made from. On older boats many tanks were steel. Condensation caused all kinds of corrosion issues, a full tank reduces that. If plastic or aluminum then whether full or empty makes little difference. Where you store your boat also makes a difference, are you in a high humid area with lots of rain, or in a relatively dry area with little moisture ??? Been a boater for over 50 years and in the old days kept my tanks full over the winter to reduce condensation. Today with ethanol fuel I just add stabil or other additive to stabilize the fuel ( it keeps moisture from forming) and keep things fresher. Many claim it is a waste of time, but.....having numerous friends from different yacht clubs in the area, it appears that those that treat their fuel have far less fuel issues than those that dont....no matter what your opinion is... number dont lie !! For the small cost of fuel additives why take a chance ??? If ten bucks for a bottle of fuel stabilazer is to costly then why do you own a boat, one of the most expensive toys you can own !!! I dont like to fix and repair, I would rather spend a few bucks for the insurance and have a fun boating season, rather than spending my season trying to fix something I could prevent. My two cents anyway !!!!!

 

[Lou C]

I honestly don't think it matters. For the last 10 years or so, I've left whatever fuel (E10) was in the tank after my last outing. I almost always add Marine StaBil (although I'm not entirely sure it really makes much of a difference, but better safe than sorry!) and usually the tank is 1/3 to 2/3 full.

I've never had a problem with any sort of moisture or condensation, my water-separating fuel filter never has any water in it, and the boat has always run fine.

We also store gas similarly at our cabin in Ontario and there has never been a problem with it, either.

Unless I'm storing equipment for more than 6 months, I don't worry about it.

I've done the same, store it with whatever is left, stabilized, and change filter in spring. Never found any water and been doing it this way a LONG time. 15+ years. This is a pretty damp climate too.

 

[QBhoy]

So here where I am…in Scotland west coast…we probably have it quite ideal for condemnation in the tank. We get hugely varying temperatures and humidity levels all through the year and especially winter. Often polar opposites within 24 hours. That was all bad enough previously…but just in the last year we have been introduced to ethanol e10 for the first time. Our normal rating of fuel is now mandatory e10 and our super is now with a warning that may be up to e5 at its worst. Many were sceptical around the idea that such a change would make much difference to things…how wrong we all were. It’s hugely affected our boats for sure. Been no end of issues caused by this. Made worse by our very unstable and constantly changing climate here. Just about most I know have sharply changed to using only super unleaded fuel in an effort to avoid issues. But aside from that, I’m of the thinking that as low as possible or empty is better perhaps. I also dose the last remaining of the tank with tcw3 oil too. Helps a fair bit, I think.

 

[tpenfield]

I usually empty the tank as much as possible, but add back some fuel for fogging the engine (MPI fogging).

Any amount of fuel is fine as far as moisture and fuel preservation. I just choose to start the next season with mostly fresh gasoline.

 

[QBhoy]

I usually empty the tank as much as possible, but add back some fuel for fogging the engine (MPI fogging).

Any amount of fuel is fine as far as moisture and fuel preservation. I just choose to start the next season with mostly fresh gasoline.

Agree. I religiously run 2 stroke through my v8 mpi before she comes out for winter. Also do the same with the much newer merc outboard. Definitely good for them I think. Pretty sure it’s actually now in the manual to do so with the mpi these days.

 

[Lou C]

So here where I am…in Scotland west coast…we probably have it quite ideal for condemnation in the tank. We get hugely varying temperatures and humidity levels all through the year and especially winter. Often polar opposites within 24 hours. That was all bad enough previously…but just in the last year we have been introduced to ethanol e10 for the first time. Our normal rating of fuel is now mandatory e10 and our super is now with a warning that may be up to e5 at its worst. Many were sceptical around the idea that such a change would make much difference to things…how wrong we all were. It’s hugely affected our boats for sure. Been no end of issues caused by this. Made worse by our very unstable and constantly changing climate here. Just about most I know have sharply changed to using only super unleaded fuel in an effort to avoid issues. But aside from that, I’m of the thinking that as low as possible or empty is better perhaps. I also dose the last remaining of the tank with tcw3 oil too. Helps a fair bit, I think.

What may be happening is that the E10 is cleaning out your gas tank and clogging filters and/or injectors. We went thru this in 2004/05. Had a red gunk in the fuel filter that year. But once the tank was cleaned out; nothing….

 

[QBhoy]

What may be happening is that the E10 is cleaning out your gas tank and clogging filters and/or injectors. We went thru this in 2004/05. Had a red gunk in the fuel filter that year. But once the tank was cleaned out; nothing….

Sounds about right. Been through a few filter changes since mid summer. Water separator pre filter and standard in line on the engine. Since also emptied tank dry. Let the contents settle and after a couple of days…was cloudy coagulation at the bottom. Now running much better, but not quite 100%. Next is the fuel rail filter and after that…an invasive dismantling of the fuel supply module, I suspect. Also have a feeling that this newish outboard and it’s running temperature so low, isn’t helping things much either…especially being ram in very cold waters here. The water she’s in averages about 7-9oC. The engine runs at about 51/52 oC 120oF roughly. Just as it should according to spec…but really cold compared to any other marine engine I’ve owned or own. Might be wrong. Oil thins very quickly and with a hint of fuel about it too. Currently probably aided by it not running too well with that fuel issue.

 

[airshot]

All the more reason to use a fuel stabilizer !!! E10 disolves all the crud that has been accumulating in the fuel system all this time. When the crap lets go you have fuel issues. Get it clean once and forall and you will be fine, the fuel stabilizer just helps work the crud through more quickly and with fewer issues. I live in an area next to Lake Erie in Ohio, all types of moisture issues being this close to the big water. Pretty much everyone with a boat uses some type of fuel stabilizer at least thru storage if not all the time to keep their engines performing well. In the spring especially, you can tell the ones that did not prepare their fuel systems, ascthey are the ones being towed in....

 

[flashback]

This thread is entertaining, condensation happens on the outside as well as inside. My old Yamaha roadstar v twin literally sweats sometimes in the morning during winter as the day warms ..dribbles of water running down the chrome covers on the engine. I spend more time cleaning than riding! Now I don't worry to much for the inside,it will boil off.

I've had a few boats (and beer) but I feed my boat, bike, and 2 strokes nothing but 100……% ..

I'm fortunate I can get it, haven't been to a marina gas pump in years, that said I don't make any long voyages anymore..a couple of Jerry cans Will do..

For 50 years I have always put my stuff to bed on reserve....

 

[tpenfield]

What folks don't consider about fuel tanks is that they are full of fumes. The fumes are heavier than air. So, moisture-laden air from the outside does not have much chance to get into the tank.

 

[tpenfield]

On the flip side . . . when I removed the fuel tank from my Formula, the way I purged the fumes from the tank was to turn it upside down and the fumes came out of the fill hose fitting.

 

[flashback]

Yep, it's a good way to sell the fuel that they don't want sitting in their fuel tank all winter..