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Author Topic:   Keeping the fuel tank full
Pat Smith posted 09-24-2000 08:33 PM ET (US)   Profile for Pat Smith   Send Email to Pat Smith  
I read on under maintenance topics they talk about fuel recommendations.They said you should keep your fuel tank full to reduce the amount of water condensation and reduce the possibility of comtamination.Does this really make a big differance?Do any of you guys do this?And what kind of comtamination are they talking about?This whaler is my first boat,so I'm still learning about them, thanks for any input.(great forum)-Pat
triblet posted 09-24-2000 11:38 PM ET (US)     Profile for triblet  Send Email to triblet     
I don't keep the boat tank full. It sits
in the garage next to my truck and I don't
keep the truck full either. But I use the
boat every weekend. If I used it rarely,
I'd keep it full. The tank will breathe
a little with changes in atmospheric
pressure. The amount of breathing is
proportional to the amount of "air" in it.
No air, no breathing. Breathing brings in
a little moisture each time it breathes in.


bigz posted 09-25-2000 06:16 AM ET (US)     Profile for bigz    
Pat I don't really know if it makes a lot of difference or not --- we never keep the 172 gallon tank on the 27 full all the time unless we are off on a cruise then it gets filled each night. Sitting at home base rarely has a full tank.

However if you don't have a water separating fuel filter on your 18 I would strongly suggest you add one regardless of how full you keep your tank --- just cheap insurance



goldstem posted 09-25-2000 02:56 PM ET (US)     Profile for goldstem  Send Email to goldstem     
I agree. A good water separating fuel filter is much more important than keeping tanks full. If you use the boat infrequently or are storing for the winter use some fuel stabilizer as well. I think the old keep the tanks full advise is outdated
tbyrne posted 09-25-2000 03:28 PM ET (US)     Profile for tbyrne    
I had an early 80's Outrage 18 and found it was CRITICAL to keep the tank full, even with a water separator. My boat sat in full sun from 7:00 am to 7:00pm on summer days and with the 10% ethanol gas required in Connecticut, made water like I couldn't believe. I had to replace the single cartridge (non-Racor) filters about once a month and still had break downs due to water in the fuel.

I suspect that I had a problem with the vent (it took forever to fill, especially after running the boat and sloshing around the fuel). Unfortunately, it couldn't be replaced easily - rusted nut and with no way to get a wrench on it.

I always carried extra filters, spark plugs and Zorb water absorber. I also made sure to keep the battery fully charged since I often had to do extensive cranking after bogging down due to water in the fuel.

Give me portable tanks any day!

lhg posted 09-26-2000 07:55 PM ET (US)     Profile for lhg    
I'm sure Boston Whaler is correct in telling you to keep a full BUILT IN tank during longer periods of non-use, especially during winter storage. An alternative is to have a completely empty tank. Non of this applies to portable, on deck, tanks.

Although water in fuel is an engine combustion problem, this is not the reason for the warning, since a water separating filter should solve THAT problem.

The problem is the alcohol spiked fuel we are now all forced to use. When combined with water, this becomes HIGHLY corrosive, and the danger is internal tank corrosion & leaking. The alcohol soaks up the water (like Dri-gas does-but never use this in a boat tank!) and sits on the bottom of the tank, corroding it rapidly. The theory is that if the tank is full, it won't collect condensation and mix with the alchohol in the fuel.

I keep my tank topped off as the weather gets cooler, and during the season add "WATER ZORB" or equivilent (this stuff emulsifies the water and it burns off in the engine, but contains NO alcohol), to the tank, then run the tank as low as possible. This hopefully gets rid of any water in the fuel tank.

Pat Smith posted 09-26-2000 10:55 PM ET (US)     Profile for Pat Smith  Send Email to Pat Smith     
Thats interesting about the alcohol.I live in North Carolina,the part of the state I live in,we haven't used alcohol in the gas for the past year or two,If they do,I'll keep it in mine.Just different climate I guess.Thanks for the input.
whalernut posted 09-27-2000 08:51 PM ET (US)     Profile for whalernut  Send Email to whalernut     
I put some in my 6gal. tanks about 2 weeks ago, should I dump this gas out(I don`t meen just dump on ground) or use it? What is the consequences if I use it? The engine is a 1975 85h.p. Johnson? Regards-Jack Graner.
triblet posted 09-27-2000 10:15 PM ET (US)     Profile for triblet  Send Email to triblet     
Would you dump it out of your car?

Chuck Tribolet

whalernut posted 09-28-2000 07:48 PM ET (US)     Profile for whalernut  Send Email to whalernut     
Chuck, what do you meen by that! I asked a serious question, as some people feel that dry gas can hurt outboard engines? Can anyone answer the question seriously? Regards-Jack Graner.
Barry posted 09-28-2000 08:08 PM ET (US)     Profile for Barry  Send Email to Barry     
Jack, What kind of tank(s) do you have? Based on lhg's post it sounds like the problem with alcohol is corrosion in metal tanks. Since the tank on my Montauk is a 27 gal. Tempo I don't have to worry about that! Obviously corrosion in a portable tank is much less of an issue than in a built in. I don't know if the alcohol has any adverse effect on the engine itself or the lines, seals, etc.
maverick posted 09-28-2000 09:41 PM ET (US)     Profile for maverick  Send Email to maverick     
I've got an 85 18 Outrage, owned it 3 years, kept the tank 1/2 full or even 1/4 full for weeks at a time, and NEVER had a problem with corrosion or water. I have a fuel/water separator on it, and I change it yearly. Each time I've taken the old one, cut it open, and looked to see what was in it - NO water - just a few particles of fine sand looking stuff. In addition, I removed the rear inspection cover of the METAL built in tank, looked inside carefully, and saw NO water in the tank vee bottom (boat was tilted up in front, too). In fact, for a 15 year old machine, the tank was literally SHINY inside, like a mirror. Now I don't run alcohol fuel (that I know of); I fill up with automotive gas (92 or 93 octane). Had 2 Montauks with big plastic tanks, same situation but not shiny metal. Just my 2 cents.
Ed Stone posted 09-28-2000 10:00 PM ET (US)     Profile for Ed Stone  Send Email to Ed Stone     
I vote for keeping the tank full with high
octane gas. Sooner or later you are going
to use the gas, better to keep it full and
be ready to go out without having to stop.
I always leave the gas cap partially open
to let the tank breath.(Avoid tank burp)
Ed Stone
whalernut posted 09-29-2000 05:02 AM ET (US)     Profile for whalernut  Send Email to whalernut     
Thanks guys, I have 2 1975 METAL 6gal. OMC tanks and use 89 octane marine gasoline at the dock. I put some dry gas in because the fuel was going to sit for a month under the mooring cover. I crack the caps a little for ventalation, just in case, don`t want the can too expand and crack, that would be a disaster. My main concern was damage by Dry-Gas hurting my outboards internal parts? Thanks again-Jack Graner.
bigz posted 09-29-2000 08:38 AM ET (US)     Profile for bigz    
Guys I might be mistaken but don't think so --- all certified portable and permanent marine gas tanks have venting built in no need to loosen the cap!

Ed I would agree with portable or smaller tanks nice to keep them filled --- when you start purchasing anywhere from 100 to 160 gallons at a pop can't see having that kind of cash @ $1.90+ per gallon laid out if the boat isn't going to be used for a while!

Now back to quality water separating filters --- we have one on each engine Racors --- interesting enough though with the boat sitting at Clarks for months with a parcel tank and then again sitting for 2 months while we fixed the dang through hull fitting up here in NJ (extracting the water which had entered the hull) there has been NO WATER in the filter bowels --- the fill up after we put her back in and did the final tune up under power on the engines was 165 gallons meaning there was about 7 gallons remaining which would have certainly brought water into the filters if any significant amount was present during the 6 hours of running fiddling with the final adjustments --- none present --

We have started to use I think it's called Store and Start I picked up at Shoreway Marine here in NJ don't know if that will do anything or not but felt it was cheap insurance, the boat does sit for up to two weeks at a time now and then --- and unlike Florida we get wild swings in temperature, felt it couldn't hurt ---

It is also my understanding on aluminum tanks which are made with 5052 alloy, just about all are since the 70's alcohol additives even with water present have no effect on them according to a friend who happens to be a certified marine surveyor --- this question was brought up when we were going over a 20 Outrage circa '78 ---

Just some of my observations for what there worth --- Tom

Lil Whaler Lover posted 09-29-2000 09:09 AM ET (US)     Profile for Lil Whaler Lover  Send Email to Lil Whaler Lover     
This is a very timely subject with winter coming on. One of my other interests is snowmobiling, which requires transporting and storing gas in portable tanks. If you get any water in the gas it is going to freeze somewhere along the (gas) line (so to speak) and then you are stopped cold. Ever try to figure out how to thaw a frozen gas line 50 miles from nowhere? Open flames are not an option. Many years ago now, several of us observed that on a sub-zero morning a metal tank that had been stored outside over night always had ice on the inside of it from condensation in the morning, but a "plastic" tank did not form any ice, even in subzero temperatures. We all switched to plastic tanks for fuel transportation and storage and that was the end of water in the gas unless, of course, the fuel supply was tainted. I do not have enough anecdotal evidence to comment on whether or not built in metal tanks react the same way in cold weather. It may depend on the amount of moisture that is available aroung the tank and how cold it is.

I would also like to echo Tom's comment about Store & Start, or StoreSafe (another product). Each outboard manufacturer has its own product that accomplishes this function, eg: OMC has 2+4 or maybe 4+2, the name excapes me right now. When laying up your boat for a month or longer, ALWAYS use a fuel preservative in the stored fuel. It is also important that your run the stuff through the carbs after adding it to the gas. It has been a wonderful preservative for me. In the last 30+ years, I have stored on average 2 outboard motors and 4 snowmobiles a year and I have yet to pay for or perform a carb cleaning and/or rebuild related to storage. It has also worked without fail on the lawnmower, chainsaw, garden tractor, weedwacker and all the other gas toys that speed up work and help provide boating time.

If it has not been your habit to use fuel preservative in stored gas start doing it this fall, it is well worth the time and $$$.

One more thing, Jack, never leave your gas cans "cracked" open for ventilation. This creates a source of fumes which could turn them into a molotov cocktail or bomb. IF they start leaking for any reason they must be replaced.
Have fun winterizing everybody. Dave

bigz posted 09-29-2000 09:37 AM ET (US)     Profile for bigz    
Dave you make some very good points --- we have always stabilized the gas in our small lawn tractor, chain saws and other assorted gas powered equipment each winter --- use a stabilizer and water absorber in the diesel tractor each time I top off the tank year round also add it to the 300 gallon storage tank even though I have a water filter on it.

The best point you made and timely I might add is WINTERIZING for us Northern folks!! Maybe JimH will add an article on the do's and don'ts since it is a very important part of keeping your Whaler or for that matter any boat and motor in top notch condition ---

Regards Tom

whalernut posted 09-29-2000 04:18 PM ET (US)     Profile for whalernut  Send Email to whalernut     
Thanks guys, my old metal OMC tanks have the old non-vented tank caps. I haven`t seen vented metal caps as an option since the eighties, if someone has a lead please let me know. If not I will purchase a couple of plastic tanks and retire the metal ones. My metal ones are in great shape, that would be a shame. Dave you said never to keep the caps cracked when moored, but the pressure builds up very high, especially with less than full tanks, and I find my tanks sometimes practically bursting at the seams, when I open the caps, it`s like a gas wind storm comeing out of there. That doesn`t seem safe either? What to do? Thanks again-Jack Graner.
Ed Stone posted 09-29-2000 09:40 PM ET (US)     Profile for Ed Stone  Send Email to Ed Stone     
Hey BigZ,
My 17 has a built in 56 gal tank and somtimes
I use 20 or more gallons per trip.Thats why
I try to keep the tank full prior to going
fishing.And living in Fla. unless there is
a Hurricane or I'm working we go out year
around. Most of the time I go out long
before daylight without a lot of notice.
Thats the last thing I want to do is
look for a open gas station at 4am.
And when the tank is full gas spits
out of the vent onto the side of my
boat and all over the plants. Thats why
I use to crack the lid on my 17.And as
far as fumes go if they don't come out the
lid they come out the vent.Now if things
work out I'll be filling a 166 Gal. Tank.
I've wondered why some of the gaurdian
brocheres claim polyethylene fuel tanks.
Ed Stone posted 09-30-2000 10:20 PM ET (US)     Profile for Ed Stone  Send Email to Ed Stone     
I've been informed that the dauntless line
of whalers comes with polyethylene fuel
tanks.That is where I seen the commercial
Whaler with a plastic tank,the new 18
gaurdian is a Dauntless.
lhg posted 10-03-2000 09:20 PM ET (US)     Profile for lhg    
Regarding alcohol/moisture problems in BUILT-IN aluminium fuel tanks, I urge anyone following this thread to go to WHALER.COM, and follow the link to "Maintainence", then "Fuel Recommendations" for an explanation of this condensation/tank corrosion problem. This is a real situation, and it is very easy to get condensation in a partially full tank as the weather gets cold. The moisture laden air gets in through the tank vent system, then condenses on the cold aluminium tank surfaces. Obviously the problem is the worst in cold months where the "dew point" becomes the issue. Cold air can hold less moisture, and the situation usually develops as a warm front, containing rain or snow rapidly moves in after cold, dry weather. The surfaces (including the interior of the gas tank - the last to warm up) of your stored boat, particularly if its in a cold garage, will not warm up as fast as the weather change, and the incoming moist air condenses on the cold surfaces of your tank.
This then drips into the gasohol fuel (usually containing 10% alcohol)in your partially full tank, combines with it, separates from the gasoline because of dis-use, and corrodes the bottom joints in your tank. When there's dew on your car in the morning, there's water accumulating in your cold, stored Boston Whaler's built-in tank! This is a good reason to pay for heated winter storage. And keep your tank full as the weather gets cold. Florida people probably need not worry about this as much, in spite of the summer humidity, because the dew point is not reached as often.

Paul Lamb posted 10-07-2000 04:47 PM ET (US)     Profile for Paul Lamb  Send Email to Paul Lamb     
Well, Let me give this a try. You're damn'd if you do and damn'd if you don't. BUT, the best reason I could give is the following. Would you store 10, 30 or 100 gallons of fuel in an open containor on your back porch for say, one week or a month or over the winter. ?? And then put it in your late model car or truck ?? And, expect it to start and perform correctly?? Even if you put in fuel conditioner in it (which prevents gum deposits ) , the perfumes (aromatics) will float away and leave you with substandard fuel. Motor manufacturers are saying to buy feul as you need it and avoiding engine problems with "stale" gas. Water in the tanks is a problem but what's a guy to do ??? Check your filters more frequently..

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