diesel stored 2 years with stabilizer and biocide, should I drain and clean tanks?

[CaptHotelIndia]

Hello,

I have been away from my boat (production catamaran with volvo Penta D2-55) for two years, and am returning to it soon. When I left it, I put enough diesel stabilizer and biocide recommended for 1 year. Obviously kicking myself now for this mistake. The engines have been run up every month or two, and the fuel is still "working" but before going back in the water shold I drain and manually clean the tanks? ...Or use another biocide to break up the growth then drain? Does anyone with experience have advice you would like to share with me? Thanks in advance. :-)

[rslifkin]

I'd see if you can pull a sample from the bottom of the tanks (stick a tube down the filler to suck it up). See what comes out. If it's sludgy or questionable, then come up with a cleaning plan. If it looks like clean fuel without water in it, then you should be good to go, just keep an eye on the fuel filters.

[CaptHotelIndia]

Thank you rslifkin. I will do that.

[JC Reefer]

Send pics of what you find!

[CaptHotelIndia]

Roger, I will.

[grantmc]

OP you could just take the opportunity to add a polishing system to your engine bay. It's relatively simple, a pump and a couple of filters. I'd expect it to be simpler and far cheaper than draining tank and having the fuel polished.

Alternatively just leaving the motor idling for a couple of hours would do a decent job of cleansing the fuel. Obviously check the filter occasionally and see what is being sucked up and poke a stick or similar down in to the tank and give it a good stir it up. Adding some fresh diesel also helps.

[roverhi]

As long as the Biocide did it's job you should be okay. Have stored diesel way longer than that and it's been good. A Cetane booster probably wouldn't hurt. Doing the above suggested inspections of the fuel wouldn't be a bad idea. Keeping an eye on the filter(s) for clean clear fuel would also be useful if you can't suck fuel out of the bottom of the tank.

Assume GrantMC's suggestion to run at idle for hours will take advantage of the fuel being recycled through the filter because of the excess fuel from the injection pump being sent back to the tank.

[MJH]

Originally Posted by CaptHotelIndia

Hello,

I have been away from my boat (production catamaran with volvo Penta D2-55) for two years, and am returning to it soon. When I left it, I put enough diesel stabilizer and biocide recommended for 1 year. Obviously kicking myself now for this mistake. The engines have been run up every month or two, and the fuel is still "working" but before going back in the water shold I drain and manually clean the tanks? ...Or use another biocide to break up the growth then drain? Does anyone with experience have advice you would like to share with me? Thanks in advance. :-)

Have you had dirty fuel problems before? When were the tanks last cleaned? What are your plans for the boat, sailing offshore?

My boat has 2x75 gal. fiberglass fuel tanks and a VP D2-55B as well. When I bought the boat in Florida the seller had the fuel cleaned because it had been sitting on the hard for four years...I still had fuel problems. Because I was going through so many fuel filters I had the fuel cleaned again a few weeks later while I was still enroute home.

In preparation for my roundtrip to Hawaii I had the fuel tanks professionally cleaned. The company emptied the tanks, opened and scrubbed them, and then the fuel was cleaned on its return to the tanks. The cost was around $1500 in 2015 and took a good part of the day.

Cleaning the fuel doesn't clean the tanks if they are dirty and rough waters (offshore?) will break it loose if it is in the tank. You don't want to discover that while offshore.

If you are not going offshore, or expect rough water, or only for a short time then just changing both the primary and engine fuel filters will probably get you by if you continue to monitor them.

Note that Biobor JF is excellent biocide but has a limited lifespan of 2-3 years from production. Check the bottom of the bottle for the production date before you buy and only buy what you expect to use within that lifespan.

Good Luck.

~ ~ _/) ~ ~ MJH

[Stewie12]

2 years is not long for diesel. If you had no fuel filter problems before that from dirty tanks there is no reason why you should have now. Fire them up !

[Scubaseas]

X2 on cetane booster. If fuel looks clear don't worry about it but do get a spare set of primary and secondary filters Add fresh biocide, check primary filter after 10 hours or if you have a vacuum gauge whenever it indicates clogging. If fuel looks dirty add biocide and polish. Diesel is pretty stable stuff. Two to three years won't degrade the fuel to the point it's unusable.

[s/v Jedi]

You have no problem, just use the diesel and inspect filters just to make sure.

[sailcrazy]

We left our boat on the hard over the summer/hurricane season. Then Covid happened, and she sat there for 19months. Not 2 years.....but close. We had filled the tank, and put a generous dose of biocide in before we left. I did run our built-in fuel polisher for about 3 hours (75 gal tank) just before we resplashed. We spent a few weeks in a marina wet slip, and I ran the fuel polisher maybe 6-7 more hours overall. She started right up, and has been running perfectly all season. Polish the fuel, then go for it!

[marcjsmith]

Had 55 gals of diesel In a steel tank(filled) ona sailboat that had been on the hard for over 8 years, minimal if any maintenance or upkeep done. No water, no bugs, tested clean, ran it all through a perkins 4108 in one season. No polishing, only went through a 2um racor.

Diesel seems pretty resilient

[wesevans]

If it was me I would have the fuel polished. That should give you a clew and clean fuel.

[CSY Man]

My dock neighbor had 20 year old diesel in his tanks.
I sold the boat for him and had the boat delivered to the Bahamas.
The engine did not miss a beat.
(The above is not recommended, but you can get away with murder, but carry spare filters, always, always..)