Tank trouble

[Andy_P]

Anyone know what type of corrosion this is? And how best to get rid of it?

It is slightly more green than is shown in the picture. It is quite spongy, and almost feels as if it could be brushed off the chain farily easily.

Bit of background info:

Newly bought, old boat. Sat for a season unused. Previous owner filled the tank with marine grade diesel, so he thought that algae would not be a problem. When I peer down the tank pipe that same green corrosion runs the length of the pipe, but the tank itself looks ok. Shiny bottom visible through the fuel, with a few black swirls that you might expect in an old tank.

We had to move the boat 50NM to its new home. No wind in the morning, so we motored for about half an hour. Then the engine cut without warning. It started again on the second attempt, and ran perfectly for another two hours, at which point we got the sails up. The engine started first time when it came to docking, and ran perfectly again.

 

[Benny17441]

It seems the green stuff is algae and the black swirl could be dead bacteria. Old diesel fuel is prone to having biological growth. Can you access the fuel pick up tube? There is a mesh filter at the bottom and it could have gotten partially clogged. That engine cut off is likely an indication that at some point in the fuel system there is a partial clog. If you can remove the pick up tube, inspect it an clean it, Inspect and replace both the primary (water separator) and secondary fuel filters. If the replaced filters looked OK and like you say the bottom of the tank looks clear then you may add a diesel fuel stabilizer. The ideal preventive measure would be to have the fuel polished. Have no idea how easy or costly would be to engage this service at your location. In any instance add a fuel additive, keep spare filters on hand and continue to be attentive to any fuel system related issues. Bad fuel can be gotten rid off but a dirty tank is something that can cause many problems. A dirty tank will usually manifest itself when you hit some rough waters causing bottom sediments to mix with the fuel and be pulled into the fuel lines.

 

[Andy_P]

It seems the green stuff is algae and the black swirl could be dead bacteria. Old diesel fuel is prone to having biological growth. Can you access the fuel pick up tube? There is a mesh filter at the bottom and it could have gotten partially clogged. That engine cut off is likely an indication that at some point in the fuel system there is a partial clog. If you can remove the pick up tube, inspect it an clean it, Inspect and replace both the primary (water separator) and secondary fuel filters. If the replaced filters looked OK and like you say the bottom of the tank looks clear then you may add a diesel fuel stabilizer. The ideal preventive measure would be to have the fuel polished. Have no idea how easy or costly would be to engage this service at your location. In any instance add a fuel additive, keep spare filters on hand and continue to be attentive to any fuel system related issues. Bad fuel can be gotten rid off but a dirty tank is something that can cause many problems. A dirty tank will usually manifest itself when you hit some rough waters causing bottom sediments to mix with the fuel and be pulled into the fuel lines.

Thanks Benny. Will investigate it today.

 

[Capt jgw]

If there is a screen on the pickup tube, remove it. You don't need it and all the filtering should take place in the primary and secondary filters. I don't know why some tank builders put those things in there, maybe they're afraid some users might not have any other filters at all, which you do sometimes see with gasoline engines. This is also a problem with some cars where they put the fuel filter in the tank. It's a $1000 job to change it, where it should be 5 minutes and $20 if the filter were outside the tank where it belongs.

 

[Andy_P]

If there is a screen on the pickup tube, remove it. You don't need it and all the filtering should take place in the primary and secondary filters. I don't know why some tank builders put those things in there, maybe they're afraid some users might not have any other filters at all, which you do sometimes see with gasoline engines. This is also a problem with some cars where they put the fuel filter in the tank. It's a $1000 job to change it, where it should be 5 minutes and $20 if the filter were outside the tank where it belongs.

Interesting. Thanks.

 

[jssailem]

Andy, I just posted this
Legend 37.5 fuel filter system upgrades?

in answer to an engine dying fuel filter issue and perhaps it is relevant here as well.

The corrosion looks like a copper sulfate corrosion. It occurs on boats when marine salt filled moisture connects with copper in a boats metal parts.


On my boat is it shows up a little more greenish blue then the pure blue of CuSO4 Likely a result of other impurities in the process


Clean it up and be sure you have a good seal on your fuel cap. Perhaps the O ring is worn or missing.

You can have someone polish your fuel (I had quotes $800 - $1200). You can rig up a filter/pump and do it yourself. (check out fuel polishing systems on the internet.) Or you can use additives (check out the Practical Sailor magazine articles regarding diesel fuel) in the fuel to kill the microbes, clean the lines and buy some extra filters to run through while you use the boat and change the fuel filter more often or when the engine complains and tries to stop. This was my strategy. I became proficient at changing the fuel filter (best time was under 15 minutes from engine cough to back running ).

I carry a couple of extra filters. I really like the simplicity of the Racor 500. Marry it with a vacuum gauge and you will know when the filter needs to be changed.

Good luck.

 

[Andy_P]

Jsailem - thanks v. much for the info. That corrosion looks very similar to ours. I found it could be removed fairly easily with a rag dipped in diesel. We inspected the tank (not bad for its age), put an additive into the fuel and and changed the fuel filters. We have an old CAV 296 filter at the moment, but Racor does seem the way to go. Another job to add to the list...

 

[jssailem]

I have seen the CAV296. I discovered they make a spin on/off alternative. Would make it less messy.

Spin On Fuel Filter Conversion Kit (CAV Replacement)

DriveForce spin on fuel filter assembly for CAV fuel filter replacement. Replaces CAV fuel filter with a spin on fuel filter conversion & spin-on element.

www.asap-supplies.com

I have been thinking about changing my on engine filter ( I call it the primary others say it is the "secondary" - tomato / tomato). The spin off might make it less messy when I have to change the filter on the engine. Also there would be less fuel to "Prime" as you can fill the filter with fuel before you spin it on..

I think I may be talkign myself into this upgrade.

The Racor is a great design. It what has sped up /cleaned up my filter changes.

 

[Andy_P]

The Drive Force looks interesting. Changing the CAV 296 was indeed messy. Made worse by the fact that the plastic drain plug snapped off - I had to loosen the whole filter assembly from the top and let the diesel run down the sides of the filter and glass bowl. The upgrade is tempting.