Diesel Tank Clean out on Bene 373

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Kinsale373

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Just gearing up to clean out the Diesel Tank on 2004 Bene 373 . I purchased 3 years ago and don't know what the inside of the diesel tank is like.

I have had zero fuel problems so this is purely prevenentative . Am I mad?

I have attached a Photo of the Tank Set up . My photo is 3.5 Meg , I t s too big for the site, I can't attach it .

Looking at the tank, my plan is :
Remove the access flandges for the Engine fuel supply and heater and pump out most of the diesel.
Because of the absence of and Inspecion cover, pump ot a sample from the bottom of the tank into an open container for inspection.
I'm considering removing the tank completely and taking it to a workshop for thorough cleaning , maybe steam clean and dry afterwards. It doesnt look to that big a job to remove the tank.
I purchased a Racor Filter/waterseperator funnel and plan to fliter the diesel before re filling.
I.m considering fitting a 150 mil inspection hatch.

Questions:
Has anyone worked on a similar tank , Will I be able to see much when I remove the existing access flanges?
Is there likely to be a baffle in this tank ?
Is high pressure water cleaning and drying advisable or overkill? Would it be better to rince the tank with clean diesel , or a mix of diesel with Bio Inhibator?

Im considering fitting an Inspection Hatch , Vitus and Henderson Tanks seem to supply them. Has anyone fiitted either ? Are they leak free? Im not sure I have enough flat space on the top of this tank to fit one?

Interested in any advise and experience,

regards, Kinslae 373
 
If you're worried about it and can get the tank out easily without wrecking the boat joinery, I'd do it. Drain the fuel, remove tank, clean and rinse it out with detergent/ hot water and thoroughly dry out. I used my ex's hair dryer to dry it out, a Vidal Sassoon Salon Pro on the hot setting for about 30 minutes.

Factor in the cost of a new hair dryer.

I did mine after a bit of fuel bug trouble, it only takes 70 litres so not a problem to start again with new red diesel, not had any hassle since. You can then not worry about if for another 16 years!
 
Kinsale373 said:
Im considering fitting an Inspection Hatch , Vitus and Henderson Tanks seem to supply them. Has anyone fiitted either ? Are they leak free? Im not sure I have enough flat space on the top of this tank to fit one?
Click to expand...

Don't risk fitting an inspection hatch anywhere other than the top surface of the tank!
 
There's not all that much benefit in getting a tank surgically clean if you're going to put ordinary diesel in it.
Far more important to check that it's 'pretty clean' twice a year than to have it perfect every third year or whatever.
I would suggest fitting a second pickup point which draws from the lowest corner of the tank (maybe on a given tack), so you can, in ten minutes, check the tank for water and remove any you find.
All hatches are a leak risk, diesel sloshing around in choppy waters will find any weakness. If you buy a hatch, whether it leaks or not may be related to whether the 'flat' panel of the tank is not really flat and stresses the hatch. Devil is in the detail and all that.
 
pvb said:
Don't risk fitting an inspection hatch anywhere other than the top surface of the tank!
Click to expand...
If it's a polyethylene tank don't fit one of the Wema/Vetus or similar ones ANYWHERE. I made that mistake some years ago. Might work well on stiff steel tank tops or rigid Tektank platics, but on slightly flexible plastic tanks it will almost certainly leak. Mine ( a Wema FLB version) leaked a LOT. Refitting with Hylomar sealant it leaked less, but still leaked substantially. Having cut a hole for an inspection hatch it took over a year and several attempts to get it totally sealed, eventually managed it with a made-up rectangular inner and outer 5mm alloy plates with about 20 machine screws plus cork/nitrile gasket plus Hylomar sealant.

On a ten year old Jeanneau tank that had had a lot of fuel through it plus occasional shots of Marine 16 I got about a pint of blackish liquid out of the bottom once I'd made a hole. It had never reached the engine or filters as the pickup tube was soem way above the lowest point.
 
jwilson said:
If it's a polyethylene tank don't fit one of the Wema/Vetus or similar ones ANYWHERE. I made that mistake some years ago. Might work well on stiff steel tank tops or rigid Tektank platics, but on slightly flexible plastic tanks it will almost certainly leak. Mine ( a Wema FLB version) leaked a LOT. Refitting with Hylomar sealant it leaked less, but still leaked substantially. Having cut a hole for an inspection hatch it took over a year and several attempts to get it totally sealed, eventually managed it with a made-up rectangular inner and outer 5mm alloy plates with about 20 machine screws plus cork/nitrile gasket plus Hylomar sealant.

On a ten year old Jeanneau tank that had had a lot of fuel through it plus occasional shots of Marine 16 I got about a pint of blackish liquid out of the bottom once I'd made a hole. It had never reached the engine or filters as the pickup tube was soem way above the lowest point.
Click to expand...
Been There!
Some of those moulded plastic tanks, the wall thickness varies a lot from place to place. And there may be 'texture' on the inside. This makes it very hard to get a seal.
A tank welded out of smooth regular sheets is much easier.
 
Thanks for the input Guys.
I think that Ill forget about adding the inspection hatch I really don't want to risk leaks. The tank is molded black plastic 120L .
As mentioned I have two 2 or 3 inch opes at the front of the tank where the engine supply hoses and Heater supply hoses are fitted. The tank is shaped to fit the bottom of the boat. (Black Plastic) Its deepest towards the front at about a foot deep. The Engine supply is right at the front at the deepest and lowest point so any crud should be below this and I should be able to access and sample from here.

I think Ill go with the plan and remove the tank completely and clean and dry before replacing. the Hair dryer sounds like it will work, !
Thanks for the ideas,

Regards, Kinsale 373
 
Kinsale373 said:
Thanks for the input Guys.
I think that Ill forget about adding the inspection hatch I really don't want to risk leaks. The tank is molded black plastic 120L .
As mentioned I have two 2 or 3 inch opes at the front of the tank where the engine supply hoses and Heater supply hoses are fitted. The tank is shaped to fit the bottom of the boat. (Black Plastic) Its deepest towards the front at about a foot deep. The Engine supply is right at the front at the deepest and lowest point so any crud should be below this and I should be able to access and sample from here.

I think Ill go with the plan and remove the tank completely and clean and dry before replacing. the Hair dryer sounds like it will work, !
Thanks for the ideas,

Regards, Kinsale 373
Click to expand...
I just purchased a 2007 Beneteau 373 and the fuel looks fine. I did have to drain several ounces of water out of it while motoring it for 11 days after purchase. My question is was draining and cleaning the tank worth it? Did you get anything out of it that would not have been handled by the large fuel filter/drain? Thanks.
 
Not sure about your boat, but AWB owner here with 160l plastic tank. I was getting paranoid after reading all the BUG chat on here.
My primary filter did look a bit slimey. Changed to a Racor copy for easier changing/inspection. New filter looked a bit grim after a season. So I built a home made polisher and scrubbed the tank as best as I could from the existing entry hole (level indicator) which happened to fall inline with the molded sump, a bit of gunk came out. Filter replaced mid season and clean as a whistle. Plenty of Marine 16 in the early days and now the one that looks like tea with every fill up (3 x this season).

If you sail in sporty conditions and your filter looks semi clean I wouldnt panic - just keep a plentiful supply of spare filters on board.
 
My tank is in the keel so cleaning it and drying it out afterwards is not practical. In order to prevent overwinter Bug I fill my tank , this protects my stainless tank from corrosion and ensures no space for moisture to enter. However I only do this after running the level right down , If I notice the engine faltering then the bottom of the tank could be sludgy so before changing the fuel filter I add petrol (older diesels only) I may use up to 33% but 20-25% is fine in the system and dissolves affected thickened fuel, then when I have time after hand pumping 2-4 liters of the fuel from the bottom of the tank with the brass stirrup pump I discard these contents at my council oil disposal point. Afterwards I pump all the remaining fuel mix into a 25 ltr tank using a 12volt car fuel pump. When finished I replace my fuel filters finally topping the diesel up before laying up. If you are suffering from water in the diesel you might check to see if the deck tank filler cap has a good seal, any doubt just get new sealing ring (green fuel resistant) water can enter from the deck especially if you have a toe rail under water.

The final step to recover the 15-20 litres petrol /diesel mix is to filter it. I syphon it using a 6mm OD tubing and gravity decant / feed it into a large funnel containing large sized coffee filters. In winter this activity might take an overnight and depending on the level of contamination you may need a couple of filters, If you find the drip speed is too slow you can drop the viscosity by adding petrol, and if you are doing it in a hot garage in summer I have used a fluid drip control (medical ) slowing the drip speed right down. Following the filter process I reuse the filtered fuel over the next season.
 
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