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captainfun 06-14-2011 08:58 AM

Best way to clean algae?
I just bought a Catalina 22, my first cabin boat. The waterline has algae and dried scum that has been on there quite awhile. I have tried some household cleaners with no luck. The boat is on the trailer on my concrete driveway. What is the best way to get the hull clean again? Is there a way to do it with chemicals purchased locally? I am 3 hours from a West Marine store.

If the best way is with marine cleaners, what do you recommend? Will I need to protect my galvanized trailer? Should I clean the boat in a sling?

After cleaning I am going to paint the bottom with antifouling paint. The bottom of the boat still has some antifouling paint on it and comes clean easily. The waterline area is where the gunk is like concrete.

Thanks in advance!

Maren 06-14-2011 09:33 AM

For a trailerable boat, a scrub brush and some bleach is a decent start, oxalic acid is good too but you need to be more careful. It will take a couple of goes at it to get it done fully.

Marine cleaners: Collinite (collinitemarine with the usual .com and such) That stuff really works and well. Make sure you get the wax too. A good cleaning and wax job will truly do wonders and will last about two years.

Galvanized trailer. Usually not. Spend the money on making sure the lights, wiring and tires are in good shape as they tend to be a bigger source of failure. Now, if it's really rusty, obviously you have to deal with that.

Antifouling paint. Think about how you are going to use the boat first. If it's going to sit in the water, antifouling paint is a fine choice. But if you launch and retrieve the boat each time and our out for a few hours or a few days, this really isn't worth the cost.

Hope that helps.

Barquito 06-14-2011 10:29 AM

If it is on the painted stripe, consider just sanding it off and repainting the stripe (Brightsides or something). Mask off the top of the stripe so you don't mess up the topsides gelcoat.

Barquito 06-14-2011 10:31 AM

If it is above the boot stripe maybe the boat wasn't sitting on its line?

JimsCAL 06-14-2011 01:06 PM

Marykate On and Off works great. It's an acid, so follow the precautions on the container. If you want to buy locally rather than drive to WM, oxalic acid from the hardware store will work also.

BBurg 06-14-2011 01:22 PM

+1 on the oxalic acid. Available at most marine supply stores. Power or sail. Spray it on and the stuff just disappears. Light brush scrubbing and that's it. Wear eye protection and gloves. I sprayed it on with a plastic garden sprayer.

fryewe 06-14-2011 01:33 PM

600 grit wet/dry sandpaper
If none of the chemical cleaners work, get a bit of 600 grit sandpaper and rub a short length of waterline to see if the discoloration will come off. If it doesn't, it has penetrated the gelcoat. If it has penetrated the gelcoat, cleaning and painting is the most practical solution.

Beersmith 06-14-2011 02:04 PM

+1 for On-Off. Stuff is magic.

captainfun 06-14-2011 05:41 PM

Thanks for all the comments. I have ordered some On-Off (the liquid kind) and some FSR that a local boat shop will have in a couple of days. I have had a couple of local guys tell me that they use Zing as well. I checked three local stores and no one has oxalic acid.

SJ34 06-14-2011 08:54 PM

Lysol toilet bowl cleaner, the gel type in the inverted squeeze bottle, works about the same as FSR but far cheaper. It's also very good at removing the stains caused by leaving bottom paint sanding dust on the deck (don't ask how I know this, I will say my neighbors Egg Harbor MY shines like a new penny).

Will second the advice to mask off the bottom paint before using this stuff. A single strip of tape rolled out slightly at the bottom (to create a drip edge) is all you need.

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