+2 for normal household vinegar(acetic acid). My boat stays in for the summer and anything stainless will get the mineral deposits. Drop the props in a bucket of vinegar, and by morning they will look as new.Upside is it is cheap. Less than 2 bucks a gallon.

wow you guys were right. what looked like a perfect grey coating was indeed just mineral deposits - looked just like a rough primer.

Used the weaker acid from home depot (they sell the good stuff outside by the way). Used the weaker stuff at full strength since the props were off. Sprayed on and by the time I picked up the hose it was already done. I would definatly recommend cutting even this stuff down to risk harming anything.

If I use CLR, vinegar, etc can I expect painted surfaces like drives to turnout ok? Or will they likely need a repaint?

I've used Lime Away at least 3-4 times a season for 19 years on the mid section of my Mercury outboard to remove mineral deposits. It still looks like new.

Mineral deposits from lake water. I have used this product for 11 years now on about 50 boats a year. It will not harm rubber bellows, trim cyc. seals or prop shaft seals and so on but will clean the heck out off any deposits baked on your outdrive, prop, rams, ect.

Its called outdrive cleaner by the makers of Nautical Ease. They tell me it is not an acid base of any sort. Don't get it on any cuts or in your eyes. Man it burns. Also important after U use the sprayer app. make sure U wash it out / spray it with clean water because it will not work the next day.

They have other products as well but I have really not used them just the outdrive cleaner and the bottom cleaner inwhich is very strong plus works well also.

www.nauticalease.com

Ask for Jim they are out of Michigan. This is the best stuff I ever used. I also sell it retail but order it thru Michigan if you like. Good luck