The mid-'80s E38 fuel tank holds 54 gallons, and for a long cruise gets topped off for max content. For me, that's fill until fuel spurts out of the air vent on the transom, a procedure that takes patience.
After returning from Hawaii I had three gallons left, and she took 51 gallons.
Then after sailing in breezy conditions (only) I noticed red fuel in the bilge.
Not much, a few tablespoons. Just enough for a heart attack. A leaking fuel tank is a nightmare which requires tearing the boat apart and probably sawing off one end of the tank just to get it out.
But that wasn't it.
The fuel sender port was weeping fuel. I remove the sender, which is inaccurate anyhow, to sound the tank. I did it three times last summer, and the five sheet-metal screws standard on fuel-level sender units no longer compressed the gasket.
I made a new cover for the sender hole, tapped the holes for better tightness and made a new gasket sealed with Permatex Aviation Gasket Sealer. Easy enough.
The point is this: With a full tank, the fuel sender port is "under water." That's because the tank cants down a few degrees at the forward end.
(In fact, the sender cannot be removed with more than 40 gallons in the tank--or it overflows.)
The leak occurred only with the agitation of sailing hard, when the sloshing fuel pressurizes the port. It didn't happen in light air or when motoring flat.
So, when filling the tank to the brim, check the sender gasket to make sure it can withstand the pressure.
And consider, as I now do, that it's pretty silly to carry around 54 gallons of fuel when half a tank gives a cruising range of almost 250 miles.
I used to think a tank ought to be kept full against condensation, but now I doubt it matters (cf. Maine Sail, et al.)
After returning from Hawaii I had three gallons left, and she took 51 gallons.
Then after sailing in breezy conditions (only) I noticed red fuel in the bilge.
Not much, a few tablespoons. Just enough for a heart attack. A leaking fuel tank is a nightmare which requires tearing the boat apart and probably sawing off one end of the tank just to get it out.
But that wasn't it.
The fuel sender port was weeping fuel. I remove the sender, which is inaccurate anyhow, to sound the tank. I did it three times last summer, and the five sheet-metal screws standard on fuel-level sender units no longer compressed the gasket.
I made a new cover for the sender hole, tapped the holes for better tightness and made a new gasket sealed with Permatex Aviation Gasket Sealer. Easy enough.
The point is this: With a full tank, the fuel sender port is "under water." That's because the tank cants down a few degrees at the forward end.
(In fact, the sender cannot be removed with more than 40 gallons in the tank--or it overflows.)
The leak occurred only with the agitation of sailing hard, when the sloshing fuel pressurizes the port. It didn't happen in light air or when motoring flat.
So, when filling the tank to the brim, check the sender gasket to make sure it can withstand the pressure.
And consider, as I now do, that it's pretty silly to carry around 54 gallons of fuel when half a tank gives a cruising range of almost 250 miles.
I used to think a tank ought to be kept full against condensation, but now I doubt it matters (cf. Maine Sail, et al.)
Last edited:
