Water in the diesel tank

wully1

wully1

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Is there a truly water tight deck diesel filler on the market?

I ran my new Beta engine today and it died after a few mins- kind of the way they do if you get air in the fuel, so I went to bleed the fuel system and all that came out was water.

So, fuel tank disconnected, water bled out, flushed through with diesel from a barrel on deck, filters changed and bled through then engine started. All seems OK.. I now have to empty the tank, clean and purge it of water then bleed everything through again. What a joyful job to look forward to.

The only place such a quantity of water could have got into the system is through the deck filler which when I think about it is fitted in a really stupid place. Water is going to be sluicing past there when sailing and rain water running past when it's raining so I want to move it. I'm thinking of modifying the inspection hatch on top of the tank when it's off for tank cleaning. Thinking of one of those fillers you see on trucks with a big neck. I'll need to fill the tank from the cockpit locker but the advantages as I see it are:

No spills to the sea.
I can see into the tank so won't over fill leading to diesel spilling overboard from the vent.
I won't have to rely on the fuel gauge.
I can brim the tank.
I will not have to worry about water getting into my fuel again.

Disadvantages : Any spills will be into the cockpit locker. It might smell a bit after fuelling up.

Anyone else done this? And does anyone have any clever suggestions for pumping out 40 odd gallons of diesel?
 
I got a racor filter for my fuel line on a beta 20hp. It does not let water through and has a drain as well. I also fill using a racor funnel which you can fill with water without it going through. There can be a remarkable amount appear in the tank from condensation alone especially in a winter like this where is is mild then cold then mild etc. I suppose you could check the filler by removing the line, building a small dam around the cap with blue-tac or similar and then putting some water there to see if it leaks. I would have thought it would be easy enough to make a waterproof deck filler even if submerged regulary.

For pumping out there are lots of cheap pumps which are rated for diesel which you attach to a drill. Ebay works. Another alternative is to seal two tubes into the tank and blow in one as the diesel comes out the other. Plumbers mate or a big wad of blu-tac can help the seal as can wet (with diesel) kitchen roll.
 
I have a simple portable polishing rig a 12 v Holley pump plus a Baldwin separator filter. Just place the suction into the tank and the outlet into a drum. For forty galls you will need several drums, then I would transfer it drum to drum to further polish it, before pumping it a third time back into the now drained (& presumably cleaned) tank.

Pics of my rig on my blogsite (below). Cost me about £50 and has been serving me well for about 6 or 7 years now, plus a new element each year. Last year I installed low point instant connectors with a return via the existing spill return system, so I can polish each tank, and I fitted extra connectors just before the installed prefilters so I can use the rig to drain or prime the fuel system at filter change time, or should I pick up a slug of muck on the fuel pickup I can blow back into the tank to clear it.

For your fuel filler plenty of good old waterproof grease on the thread each time you do it up.
 
I do not understand why diesel tanks on boats do not usually have a drain connection from the lowest part of the tank. Drain connections are standard on most other tanks for heating oil etc and boats are always getting water in the tank.
I should replace your cap but water will still get into the tank by moisture in the air in the tank condensing then running down the inside to the bottom of the tank. The air vent allows air to enter and leave as the fuel is used but also when the tank is just sitting there. Any change in temperature will result in damp air entering the tank as the fuel and air expands and contracts.
The use of fuel emulsion additives help a lot to allow the fuel to absorb the water into the fuel and prevent it from accumulating but any significant ammount of water will just sit there under the fuel ready to grow the fuel bacteria.
I have a standard diesel filler on the deck and with using the additive water is not accumulating in the tank now. I am talking from painful experience!
You should be able to pump out any water from the bottom of the tank using an engine sump oil pump which will save having to store the diesel.
Then add the additive to get rid of any remaining water.
I suggest just replace the filler cap with a standard marine diesel cap. Putting the filler inside a locker doesn't sound a good idea.
 
I agree with pub, most likely a missing or perished O ring. I check the O ring annually and give it a light smear of silicone geese and AFAIK have had no water leaking into the tank in 7 years, and my filler often has water sluicing across it.
 
Many diesel bunkers in ports and marinas are filled from barges. There is plenty of opportunity for water to get into either before you buy the fuel. Many yacht tanks have been filled from the pump with contaminated diesel.
 
vyv_cox said:
Many diesel bunkers in ports and marinas are filled from barges. There is plenty of opportunity for water to get into either before you buy the fuel. Many yacht tanks have been filled from the pump with contaminated diesel.
Click to expand...

All the more reason for having a simple and quick way of draining off the water and dirt.
 
Leighb said:
I agree with pub, most likely a missing or perished O ring. I check the O ring annually and give it a light smear of silicone geese and AFAIK have had no water leaking into the tank in 7 years, and my filler often has water sluicing across it.
Click to expand...
I use Nitrile washers & even with silicone grease i might get 2 seasons from one before it grows like a triffid
 
HunterWanderer said:
I do not understand why diesel tanks on boats do not usually have a drain connection from the lowest part of the tank. Drain connections are standard on most other tanks for heating oil etc and boats are always getting water in .
Click to expand...

I agree. I have had 4 boats, of which 3 are regarded as quality boats and only one (a Moody 31)had a drain cock in the bottom of the fuel tank. It is incredible that such a low cost necessity is not fitted in all boats
 
My boat had a new tank fitted by the previous owner. It does have a drain port fitted at the very bottom of the tank but it's got a blanking plug fitted....as much use as tits on a nun.
Once my tank is empty I'm going to run a drain hose from there,via an isolation valve or two, to a low point so I can in future drain the bottom of the tank without filling the bilge with diesel.
I'm also going to replace the priming pump filter with a Racor type filter bowl, replace the deck filler with something that work, yet to be decided...
 
Just drained my tank yesterday. It's triangular in shape with a point at the bottom with an outlet there connected to a tube with a tap in it going up to a tee which has the diesel return from the engine on the other arm. The fuel take off is a couple of inches up from the bottom of the tank. To drain the tank I disconnected the bottom line from the tee, connected it to my oil drain pump open the tap in the line and pumped it all out into a drum - about 25 litres - not worth messing about with so I filled up with new diesel.
Sailorbaz
 
I have exactly the same problem with a flush fitting deck filler. No O-rings because it is also a very strange design with angled blades which are worn. My present solution has been to remove the hose to the tank and fit a smaller diameter hose that is flexible enough to poke through the centre of the deck filler to the deck when I need it. When not in use I cork the hose and push it under the deck. A hassle but better than water in the tank.
 
My separator was full of water, and I suspected a poor seal on the filler cap, since the water was quite clear. I drained it and started the engine, only to find some very dirty water coming through. Again I drained the trap, but the water was so dirty I then suspected water contamination from the marina pump. I've duct-taped the filler cap until I can get it replaced, but if the marina supply is dodgy, that won't help. For the amount of fuel I use, I might be better off getting road diesel from the Tesco pump......
 
Tried to cure water in diesel by changing deck filler to no avail - because the problem was that water got in via a corroded tank vent (a copper tube through deck inside one of the stanchions). Are you sure the water comes in via the deck filler?
I identified the source by disconnecting both the tank vent and the filling tube and tying a plastic bag sound the bottom end of both. After a good shower, the reason was found.
 
Early last year I had both my fuel tanks cleaned by the pro's. My BSC happened shortly after. For a long time I'd had on board a Perkins glass water trap but not fitted it because I wasn't sure of the rules. I took the opportunity to ask the BSC examiner about the legality of fitting said trap. He told me there was not a problem as long as the glass trap was not inside the engine compartment. I installed it shortly afterwards, under the chart table. I can see the trap at all times and have been surprised by the amount of water that does collect. Something along these lines is to be recommended in my opinion. :) Far more acceptable than the water getting into the injector pump.:disgust:

Edited to add: 'Early last year' actually means early 2012. Well it is a new year!
 
Last edited:
viva said:
I agree. I have had 4 boats, of which 3 are regarded as quality boats and only one (a Moody 31)had a drain cock in the bottom of the fuel tank. It is incredible that such a low cost necessity is not fitted in all boats
Click to expand...

Unfortunately this is the ridiculous situation even with some Gin Palaces where the quantities of contaminated fuel can run to thousands of litres yet no easy way to drain off water lying at the bottom of the tank.
 
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