Ben Meakins gets down and dirty to discover the best bilge cleaners and the most effective way to clean oily, malodorous bilges

You can tell an unloved boat by the state of her bilges. There are many products available to clean an oily, smelly bilge.

However, before you consider the best bilge cleaners, there are environmental consequences to consider – you can’t just pump oil overboard, even oil that’s emulsified by a bilge cleaner, so you need to make every effort to capture the oily stuff and dispose of it in a waste oil bin if you can.

One solution is to use a wet vac to suck out of the bilges and contain the waste.

Once this is done and the oil is gone you can have another go at cleaning out the bilges and removing any smelly residue.

We looked at eight options, from washing-up liquid to purpose-made chemicals, examining how quickly they broke down the oil, what the smell was like and how expensive each one was.

We took a sample of oily bilge water from a boat and poured a little into a plastic cup. We then added each product at the recommended dilution and swilled each for a set time.

On draining each one we looked at the residue left behind before rinsing again and sniffing for diesel.

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Cuprinol Bilgex

Buy Cuprinol Bilgex

£11.50 PER LITRE
100ml per clean of Bilgex (which is biodegradable and highly concentrated) in 25lt of water will do for a 9.1m (30ft) yacht. It has quite a harsh smell but gave the best results, emulsifying the oil and leaving no residue behind. It removed the diesel smell effectively.

Wessex Chemicals

Wessex Chemicals Bilge Cleaner

£11.50 PER LITRE
This biological cleaner smelled fresh and works neat or diluted, down as low as 1% – they recommend using the whole bottle. It can be used as a spray/wipe-off cleaner or left over a longer period of time. Some residue remained after the first clean. The leftover smell was pleasant.

Formula 1

Formula 1 Bilge Cleaner

£12.50 PER LITRE
Fully biodegradable, this cleaner had a lemon fragrance. The manufacturer recommends pouring the whole tub into the bilge, going sailing, allowing it to work and then vacuuming out to dispose. There was a moderate amount of residue left over after one application. It masked the diesel smell well.

Yachticon Wonder Bilge

Yachticon Wonder Bilge

£23.90 PER LITRE
Wonder Bilge is highly concentrated and comes in a squeezy bottle to avoid using too much. It should be diluted at 50ml in 10lt of water. It had a pleasant, mild smell, and left a small residue behind. The diesel smell was removed well.

Starbrite Heavy-Duty

Starbrite Heavy Duty Bilge Cleaner

£14.50 PER LITRE
This had a not-unpleasant fruity smell, and its one litre should be enough for a 7.5m (25ft) boat. The manufacturers recommend pouring it into the bilge, using the boat for an hour to agitate the liquid and then pumping or draining according to regulations. It had a gloopy consistency, and left minimal residue – second best – and there was no diesel smell after a rinse.

Starbrite SeaSafe

Starbrite SeaSafe Bilge Cleaner

£12.50 PER LITRE
This eco-friendly version of the above is biodegradable, with no phosphates. One litre should treat 8m (27ft) of boat, along with 10lt of water if the bilges were dry. It has the same perfume as the above and some residue was left behind. The diesel smell was removed.


Ecover washing up liquid

We tried this as a low-cost option. It proved effective at emulsifying the oil, but left some residue behind. It would need a high concentration and the bubbles became annoying, blocking our cleaning sponge. It smelled pleasantly of lemon, but didn’t remove the diesel smell as well as the others.


Ecover Non Bio washing powder

£9.00 PER BOX
Washing powder, following a tip on the forum, had a nice, mild smell. It would be ideally used pre-dissolved in warm water for best results. It left behind the most residue of all on test, and some smell remained – but biological versions might be more effective.

PBO conclusion

All of the products tested worked in emulsifying the oil, but Bilgex (despite its strong smell) worked best, removed residue and odour, and should last for 10 bilge cleans.

As published in the December 2016 issue of PBO. Prices correct at the time of going to press.

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