Do you know what is in your tank.

[Jim@sea]

The saga of getting my engine running properly continues. (it now runs for 4 hours then stops) Thought to be air in the system. (until I looked inside the tanks)

I am getting a mechanic to re-plumb and fit new diesel pipes/hoses, new filter housings new olives on the connections to eliminate any air leakage.

So while I am waiting for him to turn up I thought I would remove my diesel tanks and clean them.

Although the boat is 30 years old the tanks are "New" Vetus plastic ones and are only 5 years old.

Had they been the original tanks removing and cleaning them would have been the first thing I would have done.

Anyway after removing the sender units I drained the tanks and was amazed at how much Black Slime "Diesel Bug" was in them. Together with what looked like small jellyfish of globulated matter which fell out in lumps into the bucket.

To think when I bought it I was going to bring it back to my home port by sea. Fortunately on the pre-purchase sea trial it broke down as we cleared the harbour entrance and we had to be towed back.

Am I naive in assuming that everyone with a diesel boat would use some form of prevention.

 

[RAI]

Yes and even with prevention the diesel bugs are on the rise aided by bio-fuel additions.

 

[PetiteFleur]

I also have a plastic tank which I fitted when I got the boat as the original steel tank was obviously leaking. After a couple of years I noticed that when replacing the CAV filter there were black sludge on the filter so ever since I have dosed with a biocide and have never had a problem since(touch wood) . My previous boat also had it and I also dosed.
From memory (the bottle is on the boat) I used MR16.

 

[VicMallows]

HOWEVER: on the basis of the above posts we might conclude that Plastic Tanks are in fact the problem

Oddly, my boat is 30 years old, the tank has never been cleaned, and I have never had any diesel problems of any kind. Something strange is going on!

 

[jollyboy]

I think part of the answer is never to allow your tank to fall below half full. If you do, the fuel sloshes around and stirs up the sludge off the bottom of the tank. Last autumn I used my Pela vacuum oil pump and poked the tube through the breather pipe down to the bottom of the (plastic) tank on my Albin Vega. It sucked up so much sludge that I felt I had to take the tank out and clean it. There was still a lot in the bottom. I guess that the reason Vic has never had any problem is because he hasn't allowed his tank to become more than half empty.

John B
Vagrant 1718

 

[Kelpie]

I know what is in my (plastic) tank because I drained it, took the inspection hatch off, and shone a torch through the side. I got it so clean I would have eaten my dinner off it.

Of course my new boat has a stainless tank so I will no longer be able to do this (the inspection bit, not the dinner thing)...

 

[prv]

HOWEVER: on the basis of the above posts we might conclude that Plastic Tanks are in fact the problem

Not at all - my stainless tank on Ariam is thick with sludge. I've been trying to hoover it out with a Pela sucker through the level sender hole, but I think this winter it's time to bite the bullet, cut an inspection hatch (which should have been there in the first place, grr) and clean it out by hand.

In Kindred Spirit we fitted a brand new tank before even launching her for the first time - and by the following winter it had **** in the bottom due to one bad fill from a fuel barge that was scraping the bottom of its own tank. At least in that case I'd specified the inspection hatch when built, so cleanout wasn't too much of a chore.

Pete

 

[charles_reed]

Not at all - my stainless tank on Ariam is thick with sludge. I've been trying to hoover it out with a Pela sucker through the level sender hole, but I think this winter it's time to bite the bullet, cut an inspection hatch (which should have been there in the first place, grr) and clean it out by hand.

In Kindred Spirit we fitted a brand new tank before even launching her for the first time - and by the following winter it had **** in the bottom due to one bad fill from a fuel barge that was scraping the bottom of its own tank. At least in that case I'd specified the inspection hatch when built, so cleanout wasn't too much of a chore.

Pete

Usually infection is from a dirty fill - fortunately I only use can and road filling stations as I'm not in UK. Mine is only a 12 gallon tank so it's easy to take it out and steam-clean (which is the only way I've found of thoroughly cleaning a tank).
It's interesting that in 25 years and 750K miles in diesel cars I've never had that problem with car tanks. Probably one of those things that you have to accept with duty-free diesel.

 

[Neil_Y]

I would always sort a large inspection hatch, my last boat had one in a stainless tank and it's very reassuring to be able to quickly check that the fuel is clean, I would check it a few times a season before passages. I never had any problems with that boat and never added any sort of treatment in 500hrs of motoring. I think cars perhaps suffer less as the fuel is replaced more frequently?

 

[prv]

I think cars perhaps suffer less as the fuel is replaced more frequently?

Exactly - higher turnover in the car itself (usually), and higher turnover in the garages' tanks.

Pete

 

[concentrik]

I'm an ex (hopefully) DB victim too. Stainless tanks and quite a large throughput of fuel. Our infestation problem only occurred when in a certain direction of swell which caused the bug jelly to climb from the bottom of the wedge shaped tank and get itself sucked into the fuel pick-up tube. Then the engine became starved as the fuel vacuum increased and the revs dropped.... which relaxed the vacuum, more fuel fuel got through and the revs rose... and so on.

We studied the test reports and performance claims for various biocide additives and tried the 'shock treatment' recommended by a couple of manufacturers. We think the shock was actually seeing the cost of the stuff, added by the bottle full. Turns out it didn't 'dissolve' or 'break up' the jelly as the mfrs said it would. It had no effect at all.

We had to cut new inspection hatches after pumping out the fuel, to get to all the furthest reaches of the baffled tank. There was loads of the stuff - no idea how long it had been building up, but we must have removed half a dozen jamjars full.

The lesson we learned was that the only way to remedy an infestation is to take out the fuel and scrub the tank, then treat the fuel with biocide. The 'shock' treatment doesn't work.

Although the prospect of doing the job was daunting it only took a few hours and was sorted the same day. A simple pump of the type you attach to a battery drill was easily capable of sucking the fuel out and we borrowed a few 25liter containers to store it on the pontoon. The fuel removed was clean and bright but we filtered it with with fine cloth before returning it to the tank after fitting the inspection covers and scrubbing the inside. There was so much biocide in the fuel after the shock treatment we reckoned no bug stood a chance in there. Some of it went in the car, too, without ill effects.

We plan to inspect visually by removing the covers every couple of months. So far we haven't had any problems. We add a preventative dose on each fuelling.