The mushroom vents on PBO Project Boat Maximus are leaking. Here, Laurie Brebner of Marine & Industrial shows us how to reseal them

Leaks are inevitable on an old boat, and deck vents are a common cause. Over time the sealant simply breaks down, there’s play in the vent and water finds its way in to the boat. From time-to-time it’s worth checking the vents and, if necessary, fixing them back down with sealant.

The two mushroom vents on Maximus, our Maxi 84, were leaking (along with a few other deck fittings) so we invited Laurie Brebner of Marine & Industrial to come down to the 43-year-old cruiser to show us how to fix them.

Tools for repairing leaky vents

You don’t need anything special to repair a vent, and it’s not expensive. Laurie brought with him a long-reach magnetic tipped screwdriver and a ratcheting screwdriver with bits in the handle.

He used a standard scraper to remove the loose sealant, though even the edge of the screwdriver and his fingers were enough to work it loose.

The area under the deck vent was very grubby. Laurie cleaned this using Wonder Wipes, which worked brilliantly. You could also use white vinegar or acetone.

Note: We may earn a commission when you buy through links on our site, at no extra cost to you. This doesn’t affect our editorial independence.

Using a sealant

For the sealant, Laurie used Sikaflex EBT+ from Screwfix, which is an excellent sealant but has only mild adhesive properties to allow for fixtures to be removed easily when required. This was applied using a standard sealant gun.

Laurie cut the nozzle away from himself using a stanley knife, at an angle of around 45 degrees. For a larger bead, you can cut higher up the nozzle.

Prolonging the life of your sealant

When Laurie finished with the Sikaflex he hung the sealant gun on the mast, leaving the dripping sealant hanging down. 

“Sikaflex has a shelf life of around 6 to 8 months but cures in the nozzle,” he said. “One trick to do with any sealant, particularly polyurethanes, is to leave the gun hanging. In not too colloquial terms, we call this bit the ‘snotter’. Sealants cure from the tip backwards, so leave the snotter on to stop them from going off.”

Laurie also suggested using masking tape around the end of the nozzle. This slows down the curing process by starving it of any air. 

How to fix a leaky vent – step-by-step

01 Unscrew the stainless vent cover and inner plastic dome 

02 Remove the vent. These holes are where the gasket tangs fit

03 Remove the gasket. This one is in reasonable condition

04 Scrape off the old sealant with a screwdriver or scraper

05 Clean the deck and vent with acetone, white vinegar or a Wonder Wipe and remove the last bits with a scraper

06 Put the gasket back in (this is the underside view)

07 Apply a generous bead of Sikaflex and squirt it in the holes

08 Screw the vent down. Note the dome will rise and fall when turned to adjust air flow

09 Screw the lid back on


Thanks to our Project Boat Supporters

Dell Quay MarineOsculatiRaymarineShakespeare MarineTruDesignScrewfixColeman Marine InsuranceMDL MarinasPremier MarinasseajetMarine & IndustrialCleam to GleamDometicWest SystemFaréclaNavigators MarineLewmarRYA


The hard sell…

Do you know any young boaters or people who dream of owning a boat one day? A recommendation from you to start reading PBO could save them money in the long run and means our experts can continue helping all boat owners with their problems.

Subscribe, or make a gift for someone else, and you’ll always save at least 30% compared to newsstand prices.

See the latest PBO subscription deals on