Seawater in tank

[marioxp]

A friend forgot to close the fuel cap on his sailboat after refueling. After that he was washing the boat with sea water and he assumes that several liters of sea water got into the tank. The tank is 150 liters.

Is this dangerous for the engine?

He is considering adding a Yachticon condensation truss to the tank. Is it a sufficient measure or does he have to drain all the diesel out?


Do you have any advice?

[Yngmar]

Yes, do not run the engine at all until the problem is taken care of. Any additive is not going to fix the problem, they can deal with very small quantities of water, not litres of seawater.

However, there's no reason to go nuclear and drain all the fuel out either. Fuel and water do not mix, the water is at the bottom, the fuel on top of it. You can simply stick a hose or pipe down the tank (inspection hatch or removed fuel take-off) and pump it out from there until only diesel comes out. Repeat while moving the hose around the lowest part of the tank on both sides.

After that you can add the water emulsifier product to deal with any small quantities of water remaining in the bottom. Check the fuel filter/water separators regularly for a while after and drain any water caught in there.

[tiger79]

I routinely pump out a litre or so of diesel from the bottom of the tank each spring, to check for water.

I use a simple primer bulb (see pic) with 8mm plastic piping attached, and a 6mm rigid metal tube connected to the suction end of the plastic pipe.  The metal tube needs to be about 500mm long.  With a rigid tube, it's very easy to "hoover" around in the lowest parts of the tank.  You may find that the tank has some moulded stiffening ribs on the bottom, and these can trap water higher up in the tank, so search around.

[marioxp]

Yes, do not run the engine at all until the problem is taken care of. Any additive is not going to fix the problem, they can deal with very small quantities of water, not litres of seawater.

However, there's no reason to go nuclear and drain all the fuel out either. Fuel and water do not mix, the water is at the bottom, the fuel on top of it. You can simply stick a hose or pipe down the tank (inspection hatch or removed fuel take-off) and pump it out from there until only diesel comes out. Repeat while moving the hose around the lowest part of the tank on both sides.

After that you can add the water emulsifier product to deal with any small quantities of water remaining in the bottom. Check the fuel filter/water separators regularly for a while after and drain any water caught in there.

Thank you very much for your quick reply!

A friend has a stupid stainless steel tank, it doesn't have a real inspection hole, but some part that is glued with some sealing compound.

I'm thinking, we should start pumping fuel through the pipe that goes to the engine, that pipe is probably at the very bottom of the tank.

Once again, thank you very much for the answer, I thought that the additive would be able to help because we calculated that 1-2% of water had entered, and after that he could start the engine normally.

[marioxp]

Does anyone know what the sealing compound used to seal the stainless steel tank could be?

If we remove this inox part, we have to re-glue it with some sealing compound, what sealing compound would be suitable, sikaflex?

[Yngmar]

The stand pipes do not go to the bottom of the tank, they stop a few cm short, to avoid sucking up the sludge and small quantities of water that are usually there. You also can't move them around, so that won't get enough of the water out.

You'll need to get into there. I don't remember which sealant is suitable for diesel, but you can look that up easily.

As it's not a Bavaria, it looks like the tank might have a flat bottom, whereas on a Bavaria it's wedge shaped and the lowest part is at the front, making it a lot easier to extract water. But you can trim the boat to pitch forward or aft as needed (dinghy on deck filled with hose). Then move your pipe around to suck up all the water from the low points.

[marioxp]

Yngmar thank you!

After I told your advice to my friend, that not to start the engine at all, my friend decided that he would not solve this problem himself, but would hire a service technician. (Although I have little faith in service technicians, you either have to tell him exactly what to do and how to do it, or it will be poorly done.)

I see now, how the Bavarias, even with the defects we object to, are quite well-built ships.

On my boat, I used one of the spare outlets from the tank to put a pipe that goes to the bottom of the tank. I haven't used it yet, I think I'll have to modify it a bit, add a piece of metal pipe to make sure it's in the very corner of the tank. My intention is to use a syringe to draw water from the bottom of the reservoir, as tiger79 did.

Thanks everyone.

[JEN-et-ROSS]

We fitted a mechanical (helix type) fuel gauge to the tank right above the deepest part..
This can easily be unscrewed, we insert a metal tube down to the lowest part, there's a neoprene pipe connecting the metal pipe to a big 1 litre clear plastic syringe that I bought on eBay...
I suck up a litre and see what's in it, any water/muck I discard, and then squirt the fuel back in... I do this fairly regularly........