I have a mystery smell on my boat which I’m trying to understand and resolve.

Everything I take off my 1978 Hallberg-Rassy Monsun 31 has this very strong, musty smell – clothing and textiles especially so, but also things made from plastic, even tools.

But what puzzles me the most is that I have never been able to smell it on the boat itself.

Toilet plumbing in the heads can be a source of boat smells, particularly if the wrong grade of pipework has been used

Having searched every corner of the internet I have come across many suggestions for curing it such as airing, ozone, bleach, hydrogen peroxide, dehumidifiers etc.

Running a fan in summer and airing as much as possible does help, but having used all of the mentioned tips the smell persists.

Whatever it is, why can I never smell it on board?

Constantin Demner

Ben Sutcliffe-Davies replies:

The smell described is very likely from a mildew or mould growing in things like headlinings and fabrics, and this is often from lack of good ventilation.

Age of the cabin linings is also potentially an issue.

So it may be worth removing a few of the cabin linings in the areas around the mast step and see if they are damp, potentially the core in that area may be wet.

Also look around portlights where possible leaks are worth investigating.

Continues below…

Best bilge cleaners: how to clean an oily, smelly bilge

Ben Meakins gets down and dirty in the pursuance of the most effective way to clean oily, malodorous bilges

Making headlining panels

The finishing touch to the interior of many boats is the vinyl-covered headlining panel, which can be detached to access…

No room for a holding tank? Use a bedpan liner

No-one should be pumping out the heads in a harbour. But what’s the alternative to fitting a holding tank? John…

Boat water tank treatments tested

The ‘tank taste’ you get from a boat’s fresh water tank can be pretty unpalatable, especially if you’re feeling seasick.…

If you can borrow a Tramex moisture meter that would be a good way to check linings that might on face value be OK but with a meter may present as being damp.

I’m aware the deck is closed cell foam, but if there is moisture in it then it will smell – which is why I’ve advised you use a decent moisture meter on the linings.

Other areas that we’ve seen before in PBO as potential sources of smells are heads hoses: check all the sanitary hoses to and from the sea toilet, holding tank and vent.

Your Hallberg-Rassy might also have a fridge drain that runs down into the bilge, and that might also need a good clean out.

Last but not least, make sure the bilges are clean and dry.

Enjoyed reading How do I get rid of boat smell?

A subscription to Practical Boat Owner magazine costs around 40% less than the cover price.

Print and digital editions are available through Magazines Direct – where you can also find the latest deals.

PBO is packed with information to help you get the most from boat ownership – whether sail or power.

• • • • Take your DIY skills to the next level with trusted advice on boat maintenance and repairs
      • Impartial in-depth gear reviews
      • Practical cruising tips for making the most of your time afloat

Follow us on Facebook, Instagram and Twitter