Below Deck Fuel Tank

[ausmike]

I have been through the mods page and can only see a few people who have installed below deck fuel tanks. This is on my mod list but I was wondering if anyone has any experience or advice on the tank construction and installation on a ... Seems there are 3 types basically Stainless Steel, Aluminum, and Plastic.

!	kmclemore:
	Corrected title

[kmclemore]

I have no speficic advice on the M... I've never seen one on an M, either.

In general I would strongly recommend you use a standard, tested and certified tank - preferably a poly-tank since they are quieter and more flexible - and place it in an enclosure which is then ventilated to the outside air (forced ventilation preferred, and indeed mandatory by some laws). The fill location should be somewhere on the boat where you could reasonably catch any spill, while also offering an easy off-boat migration for fumes. Mine is in the cockpit sole, so that I can trap any spills and effect rapid cleanup, and any stray fumes flow off the boat via the low transom.

If you do a search on this forum you'll find pics of my installation as well as links to Windarra who also has an inboard tank. Others will disagree, but I think it's one of the best mods on my boat, freeing up the cockpit storage and eliminiating messy tank changeovers. But be prepared to hear folks telling you your boat's gonna blow up one day.

[March]

It is theroetically possible to install a permanent tank below deck, car-fashion, that opens up to one side of the boat. The ventilation and the fuelling would occur through the same intake that you could cap nicely with one of those flashy marine caps that says "Fuel". However, the disadvantages far outweigh the advantages, IMO. I would not trust a plastic container shaped so as to fit the space under the rear berth. You will have to fashion a custom-made metal one, with a pipe that goes all the way up to the gunnels--big hassle. Also, if you want to refuel en route, you will still have to muck around with a plastic container that has to be stored somewhere. The tank will have to breathe, as kmclemore has pointed out. The cap may or may not allow that. An additional vent in the tank itself would allow gas vapors to seep out--not a good idea if it happens below deck. An accidental fire, God forbid, would be much more difficult to put out below deck, too. I also like the idea of remoing the tanks from the cockpit and cleaning them every once in a while.

The only advantage I can see would be, proudly fueling your boat at the gas station by sticking the nozzle into the side of your boat. You might say that the custom tank will take more gas, but I found the two plastic tanks in the cockpit sufficient for a regular cruise. (we always take an extra cannister that stays well under the cockpit seat, but we never managed to use ALL the gas on one trip...)

Not sure it's worth it even though, of course, it can be done.

[kmclemore]

It is theroetically possible to install a permanent tank below deck, car-fashion, that opens up to one side of the boat. The ventilation and the fuelling would occur through the same intake that you could cap nicely with one of those flashy marine caps that says "Fuel". However, the disadvantages far outweigh the advantages, IMO. I would not trust a plastic container shaped so as to fit the space under the rear berth. You will have to fashion a custom-made metal one, with a pipe that goes all the way up to the gunnels--big hassle. Also, if you want to refuel en route, you will still have to muck around with a plastic container that has to be stored somewhere. The tank will have to breathe, as kmclemore has pointed out. The cap may or may not allow that. An additional vent in the tank itself would allow gas vapors to seep out--not a good idea if it happens below deck. An accidental fire, God forbid, would be much more difficult to put out below deck, too. I also like the idea of remoing the tanks from the cockpit and cleaning them every once in a while.

The fuel filler is a proper, vented fuel filler on my boat, so it is automatically vented and yes, it breathes, but very safely over the back transom - not below decks. And it's not a 'flashy cap'... it's a simple, black cap, approrpriately marked.

And the tank is not just some plastic container - it is a fit-for-purpose factory made marine fuel tank, with a vent, filler, baffles, fuel gauge, grounding strap, etc. The particular tank I used was chosen because that size tank just so happens to fit nicely under the cockpit (*not* under the berth), firmly mounted on top of the rear berth in my boat (X). No custom-made tank was needed, nor would I want such a thing - I prefer a safe, tested, certified marine fuel tank, as I have installed.

Think of the millions of power boats out there today with below-decks fuel tanks... I don't really see them blowing up on a regular basis. Yes, there are fires, but 99.9% of them are because of negligence and poor maintenance, not because of the design.

I'd venture to say my boat has less gas-splash, drips and leaks (both vapor and liquid) than any other loose-tank installation. Indeed, I've had a full tank of petrol stored in the boat all winter long (+preservative), with the cabin sealed up for the season, and I'll give $100 to anyone who can honestly smell even the slightest whiff of fuel inside the cabin.

[pokerrick1]

Remove the tanks occasionally and clean them - - - another great idea I never heard before anywhere here - - - but I just happened to have done that while the boat was sitting on it's trailer awaiting insurance and launching in the Sea of Cortez when I was in San Felipe, BC, Mexico, and man, WHAT A DIFFERENCE IT MADE in looks in the cockpit Highly recommended (I think that time period was the only time I ever did any SERIOUS cleaning on my Mac - - - the rest of the time I was too busy sailing it!).

Rick

[March]

You kind of expected people to freak out about risk of explosion, didn't ya?

With a regular marine tank that fits in nicely, sure, why not? I would give priority to a permanent water tank below deck though. They make neat caps that spell out "Water" too. But if you already have that one, a permanent gas tank would come next in line--after a permanent waste tank, maybe...

[kmclemore]

You kind of expected people to freak out about risk of explosion, didn't ya?

Yes, and I objected to it, given the person who commented never even looked at my installation to know the kind of engineering and high-quality materials that I used.

The post with the details is here:

http://www.macgregorsailors.com/forum/v ... 796#p96796

[ausmike]

I agree with kmclemore, the only kind I would ever consider is a commercially available, tested, proven and approved type. And they come with deck fillers, vents, guage electronics and all approved hoses ready to fit too. Seems almost a no brainer when you apply some common sense and careful planning. So my question is perhaps not wether I should (I want to free up the current fuel lockers for other stuff that should be stored up there like propane tanks, spare fuel, etc). There are plenty on the market and seems to me any size and shape you can almost imagine, so finding one to fit the appropraite space won't be hard.

My intention would be to fit it right at the back of the aft berth, ala one done by Jack Sparrow and kmclemore. Just wondered about the type of construction material used in them ...

BTW this is such a cool site, so many good ideas and great people with them...

[K9Kampers]

How about using a beer keg for a tank, like some do on custom hot rods? Of course, you'd need to know which is which cause the other one is plumbed up to the tap on the helm satation!

[March]

I still find it intriguing that you allow for people to.....

...disagree, but I think it's one of the best mods on my boat, freeing up the cockpit storage and eliminiating messy tank changeovers. But be prepared to hear folks telling you your boat's gonna blow up one day.

...and when they offer their humble opinion based on the specific questions the man asked, you seem to take it amiss and "object"

The man didn't ask about a professional, ready-made tank. His message mentions "tank construction" not "commercial tank installation"

By the way, I looked at your mod and really liked it.

[Night Sailor]

I can see in cases where mostly motor power is used due to local conditions, or perferring to go cruising sans mast and sails, that it might be practical to use the above deck fuel lockers for some other purpose, and have the fuel tank below. There are tradeoffs though to consider.
I think you should ask yourself this question: Will I use a full tank of gas every month or so because I motor a lot?
I have only 53 hours on my original motor in 10 years because it's only used from berth or ramp to get out to clear water for sailing. For my uses, it did not make sense to use a big, hard to clean or empty tank below decks.
As it is, I fill tanks only as I project the need and every three months or so empty any fuel remaining into my trucks. It's especially important to renew fuel frequently or keep a tank completely full because of the current ethanol content which absorbs water from the air. Even then old fuel can separate and layer. Full large tanks also equal more full time weight on board, which decreases performance whether under sail or power.

[kmclemore]

I think you should ask yourself this question: Will I use a full tank of gas every month or so because I motor a lot?

My two sons like to wakeboard and get towed on rafts. A lot.