This is what Sunbrella recommends: http://www.sunbrella.com/en_us/how/c...ops-covers.php
To clean Sunbrella while still on a boat, follow these simple steps:
Brush off loose dirt.
Prepare a cleaning solution of water and mild soap such as Woolite or Dawn dishwashing liquid.
Use a soft bristle brush to clean.
Allow cleaning solution to soak into the fabric.
Rinse thoroughly until all soap residue is removed.
May not require re-treatment depending on the age of the fabric.
If stubborn stains persist, you can use a diluted bleach/soap mixture for spot cleaning of mildew, roof run-off or other similar stains (see our Stain chart for specific recommendations).
Heavy cleaning for stubborn stains and mildew
Sunbrella fabric does not promote mildew growth, however, mildew may grow on dirt and other foreign substances that are not removed from the fabric. To clean stubborn stains:
Prepare a solution of 1 cup bleach and 1/4 cup mild soap per gallon of clean water.
Soak affected area in solution for 15 minutes.
Remove stain with a sponge or clean towel.
Rinse thoroughly to remove all soap residue.
View the Sunbrella fabric Stain chart.
Remember to protect the area around your Sunbrella fabric if using a bleach solution. Carpet or other fabrics that are not Sunbrella may have an adverse reaction to the bleach.
If a boat cover is suitable in size for a washing machine, these steps should be followed:
Use mild soap.
For heavier stains add 1 cup of bleach to wash.
Wash and rinse in cold water.
Air dry. Never apply heat to Sunbrella.
Re-treatment for water and stain resistance will be necessary after machine washing.
Re-treating the fabric
As part of the finishing process, Sunbrella fabrics are treated with a fluorocarbon finish, which enhances water repellency. This finish is designed to last for several years, but must be replenished after a thorough cleaning. Based on test results,
Glen Raven recommends 303 Fabric Guard™ as the preferred re-treatment product for Sunbrella fabrics. Fabrics should be re-treated after thorough cleaning or after five years of use.
Applying 303 Fabric Guard
303 should be applied to Sunbrella fabrics after each thorough cleaning, which typically removes the original finish and reduces the fabric’s water repellency.
Clean Sunbrella fabric, using one of the cleaning methods.
Allow Sunbrella to completely air dry.
Apply 303 Fabric Guard in a well ventilated area following instructions on the container.
Apply 303 in a thin, even coat and allow fabric to dry completely.
Apply a second thin, even coating of 303. (Two light coatings are more effective in restoring fabric water resistance than a single heavy coating.)
Note: A 15-ounce bottle provides coverage of up to 50 square feet of fabric.
For more information, please visit www.303products.com
You may have access to professional cleaning firms. In evaluating the services of a professional firm, you should inquire about a firm’s experience in working with Sunbrella fabrics and knowledge of cleaning and re-treatment requirements. DO NOT dry clean Sunbrella fabrics.
Protect the area around the Sunbrella fabric when using a bleach solution – bleach may discolor non-Sunbrella fabrics. Always rinse Sunbrella thoroughly to completely remove bleach.
Please be aware of the environment when cleaning with bleach. Bleach can have harmful effects on the natural environment around you. We do not advise using bleach if you are surrounded by a body of water or other environment that could be affected.
Sunbrella air dries very quickly. Machine drying is not necessary for Sunbrella fabrics.
If fabric has some wrinkling, use an iron, if necessary, but only on the synthetic setting. As some irons exceed the recommended temperature on the synthetic setting, test a small inconspicuous area before ironing entire piece.
DO NOT use a steamer or iron set to steam setting.
Use of bleach and/or advanced age of the fabric application may impact the deterioration of the sewing thread and other non-Sunbrella components.