i bought a boat that is a fresh water and sat at the docks for 1 month... it left a greenish film at the water line and some area...wont wash away with pressure and soap.... how do i make the bottom white again ?

Use a product called on and off. I like the gel. Put it on with a brush, let it sit and rinse off. Works great.

Rene

Go to the hardware store and get Muriatic Acid. It is about $5-6 bucks a gallon. Usually 50:50 with water will take off any stain. Use rubber gloves and old clothes!!!

Zing is the same stuff is sold at marina's, but it is about $30 a quart!

As Jmherbert said.
Works great. They have it at Home depot by me in there pool supplies(two 1 gallon containers in a box) area.
Be careful with the stuff its powerful ,you might want to where a mask.

Muratic acid is easy and cheap. I always just wet teh boat down and use the muratic undiluted. Easiest way is to get a cheap pump garden sprayer and spray it on.

It will not hurt the gel or paint at all. It will eat at bare metal on trailer and will stain your concrete. I would do it in the street if possible. The stuff gives off strong nasty vapors so stay up wind as much as possible. A big wiff will have you hacking and coughing.

Rinse VERY VERY well, especially the trailer.

i've used muriatic acid to wash the dealership floors when they are nasty... i know of the vapors !!

50/50 , spray on with garden sprayer..leave on for a few minutes...? how many ?
-rince off....

question : this will remove the algae residues, the green/brown line at the water level..... etc.. ?will it make the hull all white again ?

Try Sno-blo toilet bowl cleaner. Works great & easy to use.

Yep, it will remove all the brown coffee looking stains and algae stains. It will be all white again. You may have a slight difference at the water line, but it will be very slight. It only takes a minute and the stain will be gone. No scrubing, no anything. If it does not go away with a 50/50 mix, use it without diluting.

Go to a boat supply store and get sum stuff called (ON AND OFF) it works great John

Muriatic acid is identical and sold pennys on the dollar at a hardware store.