I have seen this grey coating on props and such but have a boat that had this applied to the rams, drive as well as the prop. Then just got in another prop that has it.

First question, what is it exactly? And whats the best way to remove???

I assume its worthwhile in the salt but here in freshwater it just kills the looks and its gotta go.

Mineral deposits, Muriatic acid will take it right off. Spray it on, let it fizz, rinse it off. You're props will look brand new in 30 seconds. I take mine off the boat to avoid getting the acid on the drives.

Are you using straight muriatic acid or cutting it?

Your kidding?! I swear it looks like its a coating. I know mineral spirits wont phase it, I'll give the acid a shot tonight.

If that is the case more props to you saltwater guys on keeping your stuff lookin' good! And here I thought a little hull discoloration from the dirty lake (fresh) water was bad lol

The works bathroom cleaner will do the trick

Use it strait from a spray bottle, rinse immediatly. You could cut it and get the same results, but the contact time is so minimal that there will be no damage to the finish.

I have gotten the same "coating" from fresh water too, and depending on how long it's been on there have been unsuccessful with works. Muriatic acid works every time and requires almost no effort.

I've always cut it 50/50.

CLR bathroom cleaner works as well.

Just remember if you have an aluminum trailer to not let the acid come in contact with it. It can make for messy black streaks on the aluminum.

CLR or Lime Away do a wonderful job on mineral deposits - and are a heck of a lot less destructive than Muriatic Acid - depending on the concentration. Besides, they're available just about anywhere.

Try vinigar (mild acid) before throwing anything more harsh at it. I use it all the time to clean my stainless tips.

Most of the cleaners are an acid base. Hydrochloric and muiratic acids are the same thing.

I get the same mineral build up. If you are on a dock or rafted to boats with bad grounding systems you will get it faster. I use acid to take it off. Hull Cleaner is about a 4% solution of acid, You can buy up to 20% acid in the swimming pool section of a hardware store or at a brick supply store. How much you cut it down depends on how much crud you have, how much you want to scrub, and how fast you can do damage to something you did not want to get acid on. I usually use about 4- 10% acid. I spray it on my out drives and have been doing so for 15 years with no problems. After cleaning rinse well with soapy water to neutralize the acid. 20% acid will instantly etch concrete and the fumes will rip your nose off. My preferred method is to take the boat for a run after cleaning, then I know it is all rinsed off really well and it gives me a reason to burn gas.