We usually only have 15-25 gallons of fuel in our 50 gallon tank at year end.
I dose it with biobor and forget about it. Also we use diesel from gas stations. No issues as it is an old-school Westerbeke
40 and can run on just about anything. We do have a nice racor
filter, and a two year old fuel tank
. The Racor
has a clear bowl where you can look in and see if there is water collected, and if so, a handy little petcock in the bottom to drain that off.
We are in Toledo in the great lakes
. Our biggest issue is in the spring. Cold nights keep the hull
block, and all other masses (like the fuel in your tank) very cool, and in the bright morning sun, a small breeze comes up as the moisture evaporates from the ground. You will see moisture condensing anywhere there is something cold. Parts
of the outside of the hull
, outside of your tank, your engine block, etc. Luckily, your tank breathes through a length of small-diameter tubing, so there is not much air movement.
THAT SAID, I stopped the practice of topping off fuel tanks (gas and diesel) about 15 years ago, because I have never had condensation issues. And I hate the weight and the $$$ sitting in a boat that is layed up for the winter.
On Bio-Diesel: Avoid it at all costs. It is not commonly available where I am, but where I work, they had some big problems with some of the boats when using biodiesel in that the filters would plug
thing is it was at the molecular level. You could not see with your naked eye what was clogging them, but they were certainly clogged. Also they had to install a fuel pre-heater for cold weather
. I understand this is common when switching from Regular to Bio, where years of deposits can come loose or get broken down.
Note: Modern high-efficiency, common-rail diesels with computer-controlled injectors must have good fuel, because at low speeds they may skip cycles (take a cylinder off line for 2 revolutions) to save fuel and reduce heat. In this case a small amount of gasoline will greatly reduce lubricity and many who accidentally fuel a modern diesel car with even a small amount of gasoline can suffer major engine issues.