Triton under cockpit fuel tanks

[bcooke]

Okay, I have started tangents on three or more different threads concerning a fuel tank under the cockpit on a Triton. I will try and redeem myself by keeping the topic alive here.

Britton, I also have the fuel tank under the cockpit as you are discussing on another thread. Nice and out of the way place for it.

What can you tell me about your tank? Capacity, mounting, shortcomings? I notice you have your fill inlet in the cockpit sole. Do you ever get water leaking into the tank?

-Britton

[MikeD]

The tank is roughly 12-14 gallons - haven't had it completely emptied and filled yet. It looks as though a bulkhead under the stern portion of the cockpit was cut out, and the tank which has flanges on the sides was mounted to that with bolts. A good solid installation. No problems with water leaking into the fuel tank - it prefers the cockpit hatch. Its location places it above the stuffing box and allows easy access to the stuffing box, shaft, and after portions on the engine. A reall nice use of otherwise dead space.

Mine is diesel. Aren't there issues with place a gasoline fuel tank below decks?

[bcooke]

Hey Mike, I forgot to post a reply in the flurry of all my other posts lately.

Aren't there issues with place a gasoline fuel tank below decks?

Well, like the placement of any other explosive material in a confined living space, yes. The big worry is the fumes. Gasoline readily gives off vapors which being heavier than air, sink to the lowest portions of the boat. When the vapors are in the correct ratio with the surrounding air (specifically the oxygen in the air), any sort of ignition, the sparks in an electric motor, or the spark that is created by the flipping of an ordinary switch or just a candle in the dark, whatever, any sort of ignition is enough to turn the boat into a firebomb.

Here is a link to a video of some high school kids lighting off 10 gallons of gasoline at night: http://www.collegehumor.com/movies/1674738/
It isn't marine related but you could fill in the details with a little imagination.

The trick then is to keep the vapors out of the boat. This is done with proper venting of the tank, leak free connections, and a decent ventilation system that would keep any vapors that start to accumulate moving out of the boat before they reach the critical concentration that leads to the Big Bang.

My imperfect recollection is that the Coast Guard regulations require double clamping on all fittings, a tank vent that leads to an outside location, all the fittings must be on the top of the tank to reduce the risk of a leak (liquid gasoline produces LOTS of vapors) and at least while the engine is running, bilge blowers to evacuate any accumulating vapors.

That all said, good maintenance can bring the risk of a gasoline explosion to managable levels. If you think gasoline is dangerous we won't even talk about the most popular cooking fuel - propane.

One of the great things about diesel fuel is that diesel doesn't give off explosive vapors. You could drop a book of lighted matches into your fuel tank and most likely nothing would happen. (I said most likely, let's not test the theory!) I have witnessed jet fuel (a more refined diesel) extinguish lit cigarettes before and I am alive to talk about it.

Thanks for the numbers. I have some number crunching of my own to do now :-)

-Britton