Top Off Fuel Tanks...

...when the boat will not be used for several months?

In the water, in Florida.

Top off: Less condensation, maybe buy at a cheaper price.

or

Nearly empty tanks: Fill up with fresh fuel right before a trip is planned. Less weight if boat has to be hauled.

Thoughts?

I am in Florida and I keep my tanks full just in case. (may need a quick get away. lol) I have a single 300 gallon fiberglass tank which should have less condensation and have never had any problems. As far as weight at haul out don't worry about it the yard takes that into account and if they are that borderline that they are worried about it go somewhere else.

Kenny

We use our boat year round but we do not top off our tanks. In fact our fuel management system leaves two of the four saddle tanks empty until the other pair is nearly empty and then we fill the empty pair, finish using the fuel in the nearly empty pair, and then leave them empty until we have drawn the second pair way down.

(The engines themselves feed from a day tank that is filled when necessary from the saddle tanks.)

So an empty pair will sit this way sometimes for half a year. All five of our tanks feed via gravity from their lowest points so when a tank is empty, it's empty. And in the 14 years we've had the boat I have yet to see any traces of water in the bottoms of Racor bowls.

I know tank condensation happens--- for example, water was always present in the fuel tanks of the planes I flew in Hawaii every morning even though they had been filled to the tabs (about 3/4 full) the evening before. But it has never been an issue on our boat in our climate.

So we prefer to leave tanks empty for long periods of time rather than have fuel sit on the boat for long periods of time. The only time we top off all five tanks is when we are going on our annual fall cruise.

The weight with regards a haulout is not an issue. The yard we use has a 35 ton Travelift and a 150 ton Travelift. Our boat full-up weighs about 30,000 pounds. We keep the water tanks (170 gallons) full all the time. We've hauled with a full load of fuel and we've hauled with a minimal load of fuel. Makes no difference to the Travelift.

Haulout weight:

I agree with you guys that with our boats the weight of fuel is no issue for the travel lifts.

I was thinking of the hull distortion when the boat is on the hard. Full tanks is about 2500 lbs extra in my boat.

I keep my tanks close to full. I have two 45 gallon tanks.

I agree w Marin on the fuel tanks. And there is some obvious benefit from not having to pack around a lot of weight for no benefit.

But I disagree about the haul-out weight. A boat sitting on blocks is bad enough w/o unnecessary weight. I make some effort to get the boat lighter just before haul-out.

I put my boat on a tidal grid not knowing the keel was not straight and wound up w 90% of the weight of the boat on one spot amidships. No bad things happened that I know of so Marin is probably right that It is not something that needs attention but on the other hand Marin thinks his all chain rode dosn't effect the trim of his boat either.

Some people think weight is akin to sin (like me) and others think it rarely needs to be considered. And of course there's probably several million others in the middle but Marin and I probably don't consider ourselves extreme but in the middle so whatever you do is probably fine. Checking for water in the fuel tanks is probably something we all should do at least until we have a history that is capable of predicting the future. Checking for water regularly and finding little or none tells us our "problem" is non-existant or of little concern. But if you want to rely on Marin and I saying it's not a problem and forget about I'd say your'e neck's out there.

If the yard blocks the boat properly the weight will not be an issue. Compared to what yards often haul and block, our little toy boats are just that. And boats are, after all, designed and built to be hauled out and blocked. They started out that way in the factory. Thinking that somehow they become weaker after they're finished seems rather illogical.

If the yard blocks the boat improperly, that's another matter.

But the yard we use not only hauls little plastic toy boats like ours but big wooden seiners and cruisers, to say nothing of 100' foot yachts, power and sail, and all the other things they can pull out with their 150 ton Travelift. I have never heard of problems with damage, twisting, or hogging in this yard. But they know what they're doing and have a lot of experience doing it.

millennium said:

...Nearly empty tanks: Fill up with fresh fuel right before a trip is planned. Less weight if boat has to be hauled.
Thoughts?

Click to expand...

That's what we just did and I agree, less weight is good. We spent 5 months on the hard. We have 2-350 gallon tanks, outboard. When we hauled, there was about 100 gallons in the tanks. I didn't want to have the additional ~4,200 lbs of fuel, or about 10% of Hobo's displacement, added as we were sitting on jack stands. We've filled and then cruised about 20 hours. I just drained the Racors and no water.

Edit: This was while we were in Trinidad during the wet season.

millennium said:

...when the boat will not be used for several months?

In the water, in Florida.

Top off: Less condensation, maybe buy at a cheaper price.

or

Nearly empty tanks: Fill up with fresh fuel right before a trip is planned. Less weight if boat has to be hauled.

Thoughts?

Click to expand...

It makes no difference. The volume of air in the tanks does not hold enough water to do any damage. And not enough that the fuel/water separators can not handle. However, if you are overly concerned about it, regardless of how much fuel is in the tanks, just plug up the vent hose while you are away.

Tom-

I do as Marin does, but while the Coot has four fuel tanks, there is no day tank.

Presently have two full tanks (took on fuel last month), and now working on emptying the other two which are about one-fifty filled.

Actually topping off your tank/tanks here in FL...if done in the cooler months of the year.. is not a really wise thing to do. When a front passes through...our temp can drop 25 to 30 degrees...maybe more... Taking on fuel then, and having the temps rise up has resulted in a lot of fuel leakage through vents....

I recently had to tape a wax paper cup under the vent of the boat next to us....he was leaking gas...had filled up...cooler day, followed by warmer....strong odor of gas and sheen on the water.... When the dockmaster finally reached him...he had to take it out and burn some fuel off...

Also had a fellow in another marina we were in...used his boat in the winter months, went back up north...and when we got some really warm weather....it was really nasty...coming from a gas boat...dockmaster freaking out...praying the CG didn't show up....

A recent thread here a few weeks ago had most experienced boaters agreeing that condensation is really not a problem.

I don't think full tanks are a problem for hauling as the boats are designed for it as long as they are properly blocked.

JAT said:

Actually topping off your tank/tanks here in FL...if done in the cooler months of the year.. is not a really wise thing to do. When a front passes through...our temp can drop 25 to 30 degrees...maybe more... Taking on fuel then, and having the temps rise up has resulted in a lot of fuel leakage through vents.......

Click to expand...

You're suppose to take that into consideration and not fill the tanks to the point where they overflow.

GonzoF1 said:

.........., just plug up the vent hose while you are away.

Click to expand...

Ever seen what happens to a small plastic fuel tank with the vent plugged. In extreme cases it will collapse. Plugging your boat's tank vents is not a good idea.

rwidman said:

Ever seen what happens to a small plastic fuel tank with the vent plugged. In extreme cases it will collapse. Plugging your boat's tank vents is not a good idea.

Click to expand...

With tape... Should have been more clear, sorry.

Diesel fuel, top the tanks.

Gas fuel , leave as close to empty as possible.

If the diesel tank has a low point water sump drain use it often, esp on your return.

Bug killer may help if the tank is gust a box of fuel , not a marine fuel tank with a dewater system.

rwidman said:

You're suppose to take that into consideration and not fill the tanks to the point where they overflow.

Click to expand...

Yep....but unfortunately there are people who buy boats....big boats...and they've never even handled a rowboat....or they are the kind that thinks common sense is "cents"....

Regarding water in a good condition fuel tank – only three ways that can happen (considering no water in tank to begin with):

1. Water sucked up from fill station tank that enters along with fuel pumped into tank
2. Filler tube that allows leakage into tank from rain, snow, sea-spray, hose wash down... etc
3. Minimal condensation on inner sides of a not filled tank from limited humidity of the air trapped in tank

With fuel tank closed tightly and no water to begin with inside the tank the amount of condensation from existing air of a not filled tank is nearly immeasurable. To a closed tank the outside air’s humidity has no bearing. Vent tube will not breathe to draw in new air unless engine is using fuel while running or there is a huge, ongoing difference in temperatures that repeatedly expands and contracts the fuel’s mass.