It all depends on how bad the stain is, how long it has been on your boat and if it's just the waterline or the whole bottom. If the stain is new this year and is not too dark and just around the waterline, one bottle should do. If its several years old or really dark then 2. If you are doing the whole hull, you might need 3 or 4.

Aurora Waterline Stain Remover is safe for gelcoat. After you get the stain out, I recommend that you clean the area with Boat Scrub to remove any residue or oxidized material before re-polishing. Use a synthetic polish like Premium Boat Shine on the hull and VS721 Bottom Coat below the waterline (unless it is painted with antifouling paint).

Waterline Stain Remover can cause streaks on antifouling paint that's why you need to protect it with masking tape and plastic. In some cases the boat owner doesn't care about the streaks because it's below the waterline or they are going to repaint. If you want to protect the integrity and appearance of your bottom paint it is advisable to protect it. Waterline Stain Remover is not a paint remover. It is amazing at removing the stain around the waterline.

Aurora Waterline Stain Remover is inhibited so it will not damage your gelcoat. You can use it as often as you need to. If you need to use it more than once a year, I suggest that you protect the bottom with VS721.

It will seal the pores of the gelcoat and if the staining is caused by chemical pollutants in the water, it will accept the stain, not the gelcoat therefore protecting the boat. It will also seal the pores against water penetration and osmosis blisters. It's pretty cheap insurance.

The only way is to heel the boat to one side so that the waterline is above the water. On a sailboat this can be accomplished by securing a line from the top of the mast to an imovable object ashore and winching the line until the boat is heeled to a sufficient angle to be able to work on it. On a powerboat it will be necessary to adjust the ballast from side to side. For example if the boat has multiple fuel and water tanks it may be possible to pump the liquids from one side to the other. Alternatively you may be able to apply weight to one side of the deck untill the boat heels over. On very large boats, these methods may be impractical and you may have to wait untill the next time the boat is hauled or dry docked.

It will be necessary to make sure that this is done on a calm day when the wave splash does not wash the area being cleaned. It may also be necessary to protect the antifouling paint at the waterline as Waterline Stain Remover will attack the antifouling paint and leave it streaky or in some cases remove it. This can be done with masking tape and sheets of plastic.

Once the waterline can be kept out of the water for 1/2 hour or so, remove any loose algae with a scrub brush or power washer. Next, apply the Waterline Stain Remover with a paint roller. Wait for 20 to 30 minutes and rinse clean. In cases where the stain has been on for a long time or is unusually stubborn, a second application may be necessary.

Waterline Stain Remover is biodegradable and breaks down rapidly when it comes into contact with water, but please be resposible when preforming this type of cleaning in the water. Do not apply more than is necessary and try not to spill any directly into the water. After it has preformed it's function, cleaning the waterline stain from your boat, it should be exhausted so that the impact on the water will be minimal.

The best method is still to haul your boat and do it on land if at all possible.

You can clean the entire hull with Waterline Stain Remover. It is recommended, and safe, for use on fiberglass. As far as quantity goes, this depends on how old and set the stain is. For your sized boat, 2 to 3 bottles will probably do for the entire hull and 1 or 2 bottles for the waterline only.

If your boat is not painted with antifouling paint, consider VS721 Bottom Coat antifouling bottom wax. It will protect your bottom much better than a Carnauba based wax. Natural waxes are organic and attract marine growth, which feed on it. The VS721 Bottom Coat will also seal the pores in you gelcoat and protect against osmosis blisters and is proven to give you better performance. VS721 Bottom Coat will not yellow your boat like Carnauba waxes and it is not greasy.

Yes, Aurora Waterline Stain Remover is very effective. Roll it on, full strength with a disposable paint roller, wait 20 minutes and rinse away the stain with a garden hose. Be sure to work up-wind. It’s smelly stuff.

After, I recommend scrubbing the bottom with Boat Scrub and applying 2 coats of VS721 Bottom Coat to protect your boat and make it easier to keep clean.

Aurora Waterline Stain Remover is an acid based cleaner and can discolor galvanized metal if it come into direct contact. It is inhibited and will not harm fiberglass. After it does its work, in 15 to 30 minutes, it has mostly biodegraded and the effluent that is rinsed away will not hurt your trailer.

If their is any concern or if the stain is below the waterline and there is a chance that you will get the product directly on your trailer, then we suggest that you protect it with plastic sheeting or garbage bags before proceeding.