Weathered Royalex, Mildewed Trim

What is the best way to clean up the weathered surface of a royalex hull? Would a mild abrasive like barkeepers friend work OK? The hull seems solid but has a rough feel to it. The boat is about 10 years old and has seen some time in the weather without a doubt.

Also I had a hard and partially unsuccessful time getting rid of the black mildew stains from some ash seats and thwarts on a boat I fixed up recently. I even tried a bleach containing house exterior cleaner, Jomax or Jobmax. It helped but only some. Would a deck cleaner be advisable. On ash that mildew gets deep in the open grain, beyond the reach of reasonable sanding.

Thanks for any suggestions.

Try T.S.P.
Tri sodium phosphate. You should be able to find it at any good hardware store, usually in the paint section. I’ve used it to remove mildew from many painted surfaces, so it should work on finished or oiled woods as well. T.S.P. is also a super degreaser, so wear rubber gloves or your hands will dry and crack.

Good luck,


As for the Royalex surfaces, I wonder
whether that dull top layer isn’t protective, like the thin surface corrosion on aluminum. You can polish it off, but the sun (and perhaps our dirty air) will start to work on your newly exposed shiny surface. The used MR Guide I bought has the same dull surface film, and I’m just leaving it as is.

good thought
I think I’ll just keep at it with the mild detergent and elbow grease, then more elbow grease with a protectant. It may well go to my inlaws and so I would like to pretty it up some. The main goal though is to get everything clean and protected. It should get stored under cover from now on.

Wash the Royalex with a mild detergent, apply 303, forgetaboutit.