How to add diesel bug treatment to full tanks

[DoubleEnder]

Asking for a friend, who has a 59 foot steel boat on inland waterways in Europe. The boat has two diesel tanks, each of 450 litres. I believe they are linked by a balance pipe and that there is a smaller, central tank, where the engine (Beta 90) takes its fuel supply. Not sure about this, and it is not directly relevant I think.
The boat has been laid up for over 2 years, with full diesel tanks.
Now, about to get going again, the owner would like to add a dose of diesel bug treatment. Very sensible. But how to help it distribute though the full tanks? Any ideas? Or should he just rely on Brownian motion....? It would be a shame if it just sort of sat in a dollop at the bottom/top of the tanks.

When I had a boat my procedure was to wait until the tank needed filling, add the bug treatment then top up with fuel. That would ensure the treatment got well mixed in. But I had a small single tank and the boat went to sea so got bounced about, helpfully mixing the tank contents.

Anyway, thoughts welcome
Thank you

 

[ChromeDome]

I'd add the additive to both tanks and let the natural circulation/return by the feed pump mix it up as you go.

 

[Bigplumbs]

Mix it into a 10 ltr can of diesel and pour it in and hopefully the movement of the boat will do the rest

 

[Bandit]

I would not pour it in neat, I normally add treatment partway through re fuelling and I rest assured that with a lumpy sea crossing it mixes well.

Personally I would put the dose into a half full gallon can of diesel give it a really good shake to mix it and then pour it into the boat's tank, much less likely to sit on the bottom of the tank.

Make sure your friend has three or four replacement primary fuel filter elements as it could well kill and displace fuel bug that could block the primary fuel filter.

 

[Momac]

I think its best to add fuel treatment when refuelling.
But better to add it by whatever means than not at all.

 

[DoubleEnder]

I think its best to add fuel treatment when refuelling.
But better to add it by whatever means than not at all.

Agreed. It’s just that the tanks are already full of fuel. But the idea of diluting it with a few litres before pouring in the Marine 16 sounds sensible. Thank you

 

[Ribtecer]

What treatment products are the best to use please?

 

[DoubleEnder]

I always used Marine 16 and never had any problems. It was a 60 litre tank on a sailing boat

 

[Lodestone]

This is an interesting read - a little dated but still valid 12 of the best diesel bug fuel additives tested - Practical Boat Owner

 

[QBhoy]

Go easy on the treatment, if you can. Often causes more problems than you started with.

 

[Lodestone]

Go easy on the treatment, if you can. Often causes more problems than you started with.

That sounds interesting - can you expand on this? What happens?

 

[QBhoy]

That sounds interesting - can you expand on this? What happens?

No worries. So it’s all too often the case that a strong or even mild dose of biocide, to a fuel system that not accustomed or introduced to such a thing previously or recently…can result in the treatment (by its very nature and design), releasing and disturbing previously dormant, nasty build up or accumulations of crap in the tanks. This ends up through the filters for a good while after…and usually causing issues at the worst possible moments. Or at the very least…just might require the skipper to be prepared and ready for a few filter changes more than usual perhaps. Known this to happen many many times. Just thought I’d mention it.

 

[emmalina]

Sample the tanks first !