View Full Version : Gasoline - How long can you keep it in the boat?

09-29-2011, 09:55 AM
I purchased my 1994 Donzi Classic 22 in October of 2010. It has a 454 magnum 365 horsepower (carb) engine. For a few reasons I was not able to get the boat in the water this year. When I bought the boat we took it for a run and with the boat still running we put Storage Seal through the system (ran 20 minutes or so on the return trip to the dock). We filled the tank afterwards with Shell 94, it took about 30 gallons to fill the tank so there was some gas in it already.

My question is can I keep the tank full and expect the boat to run in the spring of 2012? I am not sure how I would empty the tank or into what but I am looking for suggestions/advice on what to do with it.

As always any help would be appreciated. :nilly:

09-29-2011, 10:05 AM
The boat should run, but it won't run too well. The longer gasoline sits, the lower the octane rating gets since that stuff just dissolves over time. You could get the gas out by using a siphon and epmtying it out into a little gas tank. (I do that for cars, so I'm not sure if there's a difference on a boat)

09-29-2011, 10:21 AM
It's better to add the additives then the gas then run the boat to make sure the they get through the entire system.. add a fuel stabilizer like stabil (red stuff) or the like and also add an ethanol treatment( or just use stabil blue stuff) to make sure the ethanol doesn't phase seperate. The discussion on fuel winterization has two basic schools of thought one fill and top off with treatments or run the system high and dry.

with a NON ethanol fuel i would agree top off and treat. with an ethanol fuel I would run high and dry. Phase seperation is far worse than the miniscule amount of water that might accumulate due to condesation.

I would just add some more fuel treatment to the 34 added gallons and run the boat. If it is laid up already I would take it for a spin on the trailer to atleast mix up the gas and treatments. syphoning can be a bit tricky with screens and anti syphon valves.put on new filters and seperator and you should be ok in the spring.

Think it was mrfix who has his electric fuel pump rigged to empty his tank. BE CAREFUL if you use any type of pump to try and pump it out the pump must be rated for flamable liquids.

hope that helps

09-29-2011, 10:47 AM
Matty makes good sense.
Chachy recently told me some 110 Octane racing fuel has some stabilizers in it that normal gasoline doesn't have. That would make sense if the fuel is stored in drums for longer periods of time.
Actually, he said adding some to the 2 stroke gas he has for his gardening tools will keep it from turning into gel. Maybe it would work for your boat.

09-29-2011, 10:55 AM
Phase separation. Man I hate when that happens. I've seen plenty of motors brought down by that, including my own Carver last year when I didn't put sta-bil in the fuel. My own mistake.

Volvo actually issued a statement a couple years ago saying they would quit paying warranty on fuel pumps killed by bad ethanol gas. The high pressure pumps on the injected motors were dying left, right, and center when laid up for the winter without stabilizer in the fuel.

I agree though, I think you'll be OK if you treat the fuel. It won't run the best on that old gas, but it should be OK. Wost case, you might evaporate the fuel out of the carb and have to break it down for cleaning next year, but I say the odds are better than even you'll be fine.

I do tend to agree that pumping the fuel out is the best option, but it's a PITA. I've done with a cheap parts store 12v 'ticker' pump and some hose. Pop off the inspection plate in the floor, hook up to the pick-up with a short piece of hose, then run a longer piece over the side to a jerry can. If the fuel is already old/suspect, I usually try to distribute/dilute it among all my cars/trucks/mower/log spliter/etc...anything that has at least a half tank of good gas and will get used semi-regularly.

09-29-2011, 11:45 AM
This seems like a good place/time to ask a few related questions. I have a big tank of gas available, 2 years old, with ethanol. It got plenty of both Startron (the blue stuff) and Sta-bil. Maybe 1.5 times the recipe per gallon, and was well mixed. I am pondering whether it would be possible to siphon(or pump) it out and use it.

If I did, I could run it through the remote Raycor fuel filter as I pumped it out. And I could ensure that filter had the ultra-fine, 2-micron cartridge when I did.

Once out, I'd be running the gas in a boat with old, carbureted motors.

Questions as follows:
Is it just a bad idea altogether? (Skip 2 and 4)
If not, should I be blending it with new gas rather than burning it straight up?
If blending it is the right answer, any notion of what ratio might make the most sense?
If I do it and if it harms something, is it basically limited to fuel pumps and carbs, or is there anything else to worry about?
Would a 10 micron filter be any worse for this experiment than a 2 micron filter, when I pump it out?
Any other thoughts or advice?


09-29-2011, 02:20 PM
what does available mean? someone giving it to you? or is it a tank you have to deal with?
if it is free I would pass on it. If it is something you have to deal with or empty I would pump out small amounts and visually inspect it. you're looking for orange juice,water, and junk. use an inline filter on the pump or syphon hose and also double or triple up the screens in the portable gas can you dump the gas into . If it looks ok I would mix/blend at a 1 to 4 ratio . if I was filling up the car 25 gallons I would dump 5 old to 20 gallons new . As Zel said I would also mix it in with stuff like lawn mowers and leaf blowers as long as it will go in the tank and be burnt at once not lay around. I would not put old gas in a boat tank. the ethanol also breaks up junk in the tank and it loves old rubber.So I would make sure the fuel system is up to date especially the lines ,seals and hoses.

09-29-2011, 03:18 PM
Thanks Matty, that's VERY helpful. It's something I have to deal with--my Nova Marine that needs me to drop another smallblock in one side. I have 85 gallons of pure joy to take care of. Figure there ought to be some way to make good use of it.

The Cig is getting ethanol gas now (no choice in MD) so I figured I'd replace the fuel lines at least.


09-29-2011, 06:19 PM
It will be fine, you will never know.

09-29-2011, 06:41 PM
I wouldn't worry about it. At least you put additive in the fuel. I had the same motor and filled it to the gills

when winterizing to keep the tank from sweating. That 454 Mag is very forgiving. Run it in the spring to half

or less and top it off with fresh.

09-29-2011, 06:54 PM
The Cig has a pair of inline 6 292s. I'm hoping they as forgiving as the 454Mag that Offset has. :) -Mike

joseph m. hahnl
09-29-2011, 07:41 PM
If I understand correctly this boat has already been in storage for a year with the gas in it. Your question is will that fuel that sat for a year be OK. Geographical area plays a big part.In places like Florida that have high humidity ethanol fuel has 2/3 less shelf life than say in the northern states. The typical shelf life of ethanol fuel with out treatment is 90 days with light to moderate humidity.Places in the dessert like Arizona fuel may last longer, as the air is virtually dry. The fuel becomes saturated with water.This fuel will still work if a anti Phase separation additive was used. As much fuel as possible should be removed if you didn't use a phase separation stabilizer. If you fill 5 gallon cans, You can use it confidently , if you live in a freezing climate and you let the water freeze and drain of the good gasoline. "Yes this does work" but use it in simple engines.

So here is the shock factor it only takes 0.5% water 3.8 teaspoons per gallon for phase separation to occur in unconditioned fuel.

When phase separation occurs it forms three layers.
The clean fuel is on top, the clear water is in the middle, and the corrosive brown layer is at the bottom.

Obviously you know the hazards of any flammable liquid.

So ask your self. How can I tell if this has happened?
You need to take a sample of the fuel from the very bottom of the tank. One way this can be done by disconnecting the fuel line from the water separator, have an assistant turn the key on , the electric fuel pump should turn on and you can fill a mason jar with a sample.

One Thing to consider if you have to evacuate the gas tank. It is feasible to only have to drain off the lower part of the tank to get clean fuel. Most people just take it all out.

But it is theoretically possible to just remove the contaminated lower layers. Although, there is, the potential for residual contamination to remain . The best way to do this is to use the the tanks gas line and not a siphon hose through the top. In theory the good gas will force the contamination out . You want to bleed it clean. Just make sure you don't agitate the fuel.

09-29-2011, 07:48 PM
I am running last Octobers stabilized fuel due to a very wet summer, boat is running fine but I did pickup some water. It was the first year I did not tightly tape my vent, I think taping the vent helps to control moisture getting into the tank during storage.

09-29-2011, 07:56 PM
Thanks. This info helps a lot. Bad news is I didn't tape the vent and the boat will get a bit of sloshing with the forklift. But I can let it sit a couple of days before I move any fuel out. Good news is it had lots of stabilizer and ethanol treatment, and it was SUPER full. Meaning, the exposure to air/humidity should be the cross-sectional area of the fill line (a few square inches), not the full area of the top of the tank (maybe 8 square feet).

09-29-2011, 08:06 PM

i am a little lost with the water seperator comment, does a merc have two pumps?isn't the filter seperator in front of the pumps? stopping junk from getting into the pump.wouldn't you want to take off the hose from the carb or FI after the pump? my setup goes tank, filter, seperator, pump, carb is the merc different?

09-29-2011, 08:42 PM
one year on the fuel is one thing,,, but two,,, i just siphoned out 50 gals out of my maritime skiff, i also didnt use the boat this season and did not use it much at all last year, the fuel smelled funky, but i ran my Honda around for a few weeks now with no problems,,, yet,,, i think its better to have the fresh fuel in the boat only because of a possible break-down issue

09-29-2011, 10:38 PM
I roached my 383 with bad gas. Seems water won't combust like gasoline does. That's what the machine shop tells me. Also the baffels get in the way when removing the gas so bounce the boat when your draining.

09-29-2011, 11:30 PM
Me personally, I'd drain it all out and start over. I'd pull it from the bottom of the tank too, not go in from the fuel cap.

Phase separation...ugghhhh... I roached two ktm 300 2t motors this summer because of that ethanol crap. Going WFO under heavy load both times (riding in sand and I weight 225) The first time I stopped before REAL bad damage when I heard that marbles on a piston noise. The second time, I must have really had a lot of h20 in the gas, was running pinned in 4th and CLUNK, the rear end locked up on me. The skirt of the piston broke and fell in to the big end and go stuck in the transmission. Ugly... Now I only mix and pour in what I use any time I go riding.

For my boat, I am lucky enough to get REAL gas but it's only 87. Just because I'm freaked out and somewhat gunshy, I use that startron stuff. My old Benz runs better with the startron in the tank. I can actually FEEL the difference, mainly in starting of the motor.

fyi, for guys who trailer thier boat, you can find locations of "real" gas at www.real-gas.org

09-30-2011, 02:07 PM
>was running pinned in 4th and CLUNK, the rear end locked up on me.

oooohhhhh....bet that got your attention!

Only time I've accidentally locked a rear wheel was on my Speed Triple. I'd just ridden almost 70 miles of highway coming to work and was at a stop light a couple blocks from the office. I took off a bit 'aggressively' and lifted the front tire a few inches. I got about half way across the intersection before the tail bag I had strapped to the pillion came loose and caught on the top of the rear tire where it promptly wedged between the tire, exhaust, and sub-frame. Not only did it bring me to a STOP, but I was stuck sitting in the middle of the road with a bike that I couldn't move! I finally managed to rock it backward enough to get the bag out, but trashed a carbon fiber muffler and rear hugger, not to mention a Tourmaster bag.

And that was at maybe 20 mph...

joseph m. hahnl
09-30-2011, 04:39 PM
am a little lost with the water separator comment, does a merc have two pumps?isn't the filter separator in front of the pumps? stopping junk from getting into the pump.wouldn't you want to take off the hose from the carb or FI after the pump? my setup goes tank, filter, separator, pump, carb is the merc different?

I was assuming because it was a 1994 it had an in-line electric fuel pump before the separator with fuel injection. But apparently it is not Fuel injected. It's the same as you described as is mine. So I think the best way to do it is to disconnect the rubber hose coming from the gas tank, from the separator and install a inexpensive electric in-line fuel pump . I would recommend that it should be hard wired to the ignition and bonded to the block so there would be no chance of arcing. Which could happen if you tried to hot jump the pump. Gravity would probably work too if you coupled a longer hose "again to the gas tank rubber hose" and ran the longer hose out the drain plug hole in the transom. You want to minimize the amount of contamination through the fuel circuit,that is why I suggested to do it at or before the separator.

The more I think about. The better it is to couple the long hose out of the boat and keep the gas spillage and fumes to a minimum in the bilge. This method would also allow the use of barbs with the coupler and the tank gas line fitting and a barbed fuel pump out side the boat. This would be much safer and easy to rig.

10-02-2011, 08:26 AM
Thank you to everyone who responded to my question concerning gas storage. I am still not quite sure what to do but if I leave the gas in I will let you know in the spring what if any issues come up.

I am hoping that what is in the boat is straight gas, the guy I bought it from kept it in a boat house so the gas he bought was always from a marina that sells only straight gas. Maybe wishful thinking but that is my hope.

Again, thanks to everyone for taking the time to help me out with your suggestions and experiences.