Scum Line

[hd79irnhrs]

HI can someone suggest a good product or way to remove the scum line of algae from my hull. I power washed it ,then scrubbed with a brush and liquid soap for boats but but it doesn't want to come off! Boat was supper clean when put in one month ago but the algae is so bad this year I pulled her out to power wash it.She is in fresh water (Saginaw Bay Mi) and it has fresh bottom paint,but I have a 2 inch scum line above the paint.Also the bottom paint wanted to flake of on the top edge.I am assuming it wasn't prep ed right at time of painting.I just purchased her last month and the owner before me took extreme pride in her up keep and I intend to follow suit.Any suggestions why the bottom paint wants to flake? thanks Greg

[231CALIFORNIA]

The pressure washer might have done a bit of it but either preparation or paint adhesion qualities  may have something to do with it.
bottom paint is often "ablative" meaning  i think that it sheds intentionally but not normally all at once. It has to be re apllied . I think that when they removed Copper from bottom paint and replaced it with I think? tin? it isnt as effective anymore  but pollutes less. if it is hard calcium or similar stain you need an acidic cleaner I think, if it is Green chlorophil you need and oxidizer / bleach containing cleaner. Im sure that the locals in your marina will know what to do with the local scumline stain and your marina store will ahve the cleaners.
woudl it have helped if the bottom paint wast up the side 2-4 inches more?

[hd79irnhrs]

The bottom paint had tiny flakes still adhering to the boat on the top edge but then the power washer blew them of instantly.I think it wasn't quite prepped right so I'll learn that process this fall after she comes out for the winter.I also am going to raise the paint line. I will give a diluted bleach with water a try. thanks for your reply Greg

[togators]

I do not know what this will do to bottom paint, but I use Rust Aid for yellow bottom stains on the fiberglass.  I put it in a sprayer, brush lightly, rinse.  Just did my bottom after she sat in brackish water for about a week and she looks brand new.

[hd79irnhrs]

Hi thanks for the reply!This rust aid is it a boating product or is it like iron out,or lime away? Have never heard of rust aid thanks Greg

[togators]

Rust aid is like iron out I think.  Sold at Home Depot for $10/gallon.  I did my 23 with about 1/2 gallon in about 20 minutes.

[ppaulg]

Ablative paint is designed to wear off slowly like a bar of soap. If the boat is not used enough and the outside layer does not wear off and it stops working.

A hard bottom paint will flake off and the biocides in it constantly come to the surface whether the boat is used or not...

[gjvp]

Greg -
It sounds as if your waterline is too low for the boat's loading, and as a consequence she's riding above the bottom paint and allowing algae to grow.  Algae don't grow on a moving -i.e. water-scrubbed - bottom. 

You might be able to make some reference marks bow, stern and anywhere in between you can reach from the dock or a dinghy in absolutely calm conditions.  That will give you the true waterline with the loading you're actually carrying.

If it's above the current bottom paint, that's your problem. It's at least helpful next year when you're repainting the bottom.

Another factor is the type of bottom paint. Most of the people in the fresh water of Lake Erie - particularly the racing sailors and powerboaters who watch their fuel consumption - use Interlux VC17 Extra.  It's not an ablative paint; it doesn't need to be.  The season's only six month's long and freshwater doesn't support the kinds of growth that proliferate in salt water.

Maybe discover what kind of bottom paint is on your boat, and where the true waterline might be.  Then you can start finding solutions.

Greg

[hd79irnhrs]

Thanks I intend on raising my bottom paint line at least 2 inches.With 135 gal fuel tank it sets her down with 4 people and fishing gear.And then theres that darn beer cooler! take care greg

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