I have a 1995 Catalina 36
Mk II with a surprise fuel tank
. The survey
report indicate one fuel tank
, the manual reports one, and when I went to fill the tanks
I discovered two deck-fills, and two fuel
vents, and when the boat bounces at sea, one of the fuel
vents sputters diesel
I investigated further, and found that a small storage
compartment had been replaced with another 20 gallon tank. The new tank is directly below the original tank.
The fuel drain from the upper tank T's into what appears to be a fuel drain from the lower tank before going (combined) to the Racor
filter. I say "appears" there because the "drain" is on the top of the lower tank. I'm guessing that the "drain" contains a tube that runs to the bottom of the tank such that it can be sucked out. There is also a hose running from the injector assembly of the aft-most cylinder back to the top of the lower tank. I have no idea what that hose is for. The lower tank also has its own fuel vent line (on the top).
I'm guessing that as long as there is fuel in the upper tank, the lower tank will be completely full. Fuel will drain from the upper tank into the lower tank, displacing the air that will escape through the fuel vent. The fuel will then flood into the tank vent and rise until it is at the level of the upper tank.
This system is problematic because it appears as though the lower tank will almost always be full, and diesel
will always spill out of the fuel vent. I also have no idea what that second hose is running from the engine
to the top of the lower tank.
Does anyone know what the second hose might be?
Would it be reasonable to place a fuel valve on the lower tank's vent line such that diesel does not spill as the boat tosses?
When (not if) I forget to open the vent valve before motoring or a hot-summer day, would that represent a hazard?
Can anyone recommend some good reading to better understand things? I'll be looking into books
diesels in general.