I've actually washed foam mattresses with soapy water (important not to use too much detergent) and then man handled (am I allowed to say "man handled" these days ) them into the washing machine and put on the spin cycle. Or you can leave them sitting on the clothes line for a week to dry out (good weather needed of course). It all depends on the size of the mattress and if you have plenty of fresh water to rinse the detergent out and then some where to dry it back out.

I've never heard of any miracle spray or easy fix especially if the mattress has any salt build up in it.

My memory foam 7inch topper smelt lovely like rubber when it was new.....
now it smells like Cats wee and I have my forward cabin shut down ...
I tryed washing it but it was like a big sponge and took weeks to dry.
I have been looking at getting a custom innerspring made by "making mattress" but I see no point untill the cat works out its not a toliet

FWIW when I hire a carpet shampoo machine I give the boat foamies a go too . Leaving them to dry in the sun. Never use the commercial detergent, Google Shannon Lush carpet cleaning recipe, it has eucalyptus, clove oil etc. Comes up very nicely.

southace said..
My memory foam 7inch topper smelt lovely like rubber when it was new.....
now it smells like Cats wee and I have my forward cabin shut down ...
I tryed washing it but it was like a big sponge and took weeks to dry.
I have been looking at getting a custom innerspring made by "making mattress" but I see no point untill the cat works out its not a toliet

This would be a significant deal breaker in my relationship with the cat!