Pressue wash on yellowish stains on deck

[Adetheheat]

Before I take my pressure jet wash to the marina does it work at removing stains on the deck and making it look clean again?

 

[ChromeDome]

That depends 100,7% on what the stains are.

Pressure wash may work - or not.

The proper way with unknown stains is to start mild and gradually go to more aggressive weapons. If it can't be dissolved or otherwise removed, bleach might be the way. Oxalic acid is a natural compound in rhubarbs, still to be used with care on non-white surfaces.
Ultimately wet sanding with 1200 grit, then rubbing, then polish.

High pressure is only one property of water being output by a pump. The nozzle design is what makes the difference. Make sure you have a rotary nozzle at hand when attacking stubborn dirt.

 

[jwilson]

Be VERY careful with pressure washing decks. If a teak deck it can almost destroy it if used too close. If not teak then it can find (and maybe create) leaks. It can even open up hidden voids in GRP. Start with soft brushes and detergents, go to oxalic acid for brown rust stains. I have a pressure washer, for nearly 20 years used it annually on the underwater hull, I've never let it be used on deck.

 

[johnalison]

I would start with an oxalic acid product, but birds sometimes leave yellow stains and these don't need treatment. If you wipe the actual guano off the residual stain will disappear in a few days.

 

[[70521]]

Before I take my pressure jet wash to the marina does it work at removing stains on the deck and making it look clean again?

some soap and elbow grease, if that does not work then move onto something stronger.

 

[Stemar]

Be VERY careful with pressure washing decks. If a teak deck it can almost destroy it if used too close. If not teak then it can find (and maybe create) leaks. It can even open up hidden voids in GRP. Start with soft brushes and detergents, go to oxalic acid for brown rust stains. I have a pressure washer, for nearly 20 years used it annually on the underwater hull, I've never let it be used on deck.

Big +1

I blew holes in the gelcoat of a friend's bat cleaning it with a pressure washer. Not structural, of course, but unsightly, and you never get an invisible repair.

My goto for that kind of thing is oxalic acid; a tub from eBay lasts a lifetime. Another thread suggests Harpic or similar, but I haven't tried that.

 

[Adetheheat]

I used the pressure washer. It seemed to work OK with no damage

 

[johnalison]

I used the pressure washer. It seemed to work OK with no damage

It should be OK on a sound boat without bare wood. I read once that Malo pressure-wash their boats to look for leaks, and if one is found the person who fitted the faulty item has to redo the job.