Acid washing growth off fiberglass bottom in Fresh water????

badcarma58

Seaman Apprentice
Joined
Nov 15, 2010
Messages
33
I have a trailerable center console boat.
The boat does not have bottom paint. It is bare fiberglass.
I had the boat in the water (fresh) all summer, and got quite alot of growth.
I pulled the boat, powerwashed as best I could, but the crust remains on the bottom.
I've tried some Starbright products, but they don't really work at getting the fiberglass clean.

What can I use to get my hull clean again, without sandblasting?

I called a couple of marinas in the area, and they don't acid wash anymore due to EPA regulations.

Any suggestions? I am in Western end of Lake Erie, in Toledo Ohio area.
 

Rentaltux

Seaman
Joined
Dec 8, 2010
Messages
72
Re: Acid washing growth off fiberglass bottom in Fresh water????

I wash mine down every fall with a deck cleaner from Behr, works great. I would say anything with oxalic acid would work. I use a little hand pressure sprayer and you can watch the gunk come off almost instantly. Then I use my pressure washer to rinse. Sometimes you might have to touch up a couple stubborn areas but it is the only thing I have found to work so well. I wet everything down first before applying and avoid any galvanized metal areas on the trailer. If I get some on I just rinse off right away. It doesn't like some metals.

R
 

wgl333

Petty Officer 2nd Class
Joined
Jan 11, 2011
Messages
140
Re: Acid washing growth off fiberglass bottom in Fresh water????

On and Off Bottom and Hull Cleaner....spray on (I used a garden sprayer)....scrub brush the real heavy areas...and then power wash off....works great...gloves and a mask though....
 

sludgeguy68

Petty Officer 2nd Class
Joined
Jul 16, 2010
Messages
111
Re: Acid washing growth off fiberglass bottom in Fresh water????

I had the same issue, used Muriatic (AKA Hydrochloric) Acid mixed with water, worked pretty good and is almost half the price of listed products ($16/gal). It reacts with some metals though (don't use on galvanized trailer)... I rinsed everything off extra well.
 

calvinator

Petty Officer 1st Class
Joined
Sep 22, 2010
Messages
286
Re: Acid washing growth off fiberglass bottom in Fresh water????

I'm in Lake Erie too. x2 on the 50-50 muratic acid/water in a pump sprayer. Power wash off.

I use this on my fiberglass boat and the outdrive. I also use it on my pontoons and outboard motor.

I do cover my painted trailer with plastic sheeting before.
 
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crabby captain john

Lieutenant Commander
Joined
Aug 6, 2011
Messages
1,823
Re: Acid washing growth off fiberglass bottom in Fresh water????

Muriatic Acid -- I don't mix with more than 10% water. The gunk rolls off and usually a garden hose takes care of the rinse. Maybe a couple stubborn places need some rubbing. Everywhere it touches it removes wax and everything but makes for a clean hull.
 

Thalasso

Commander
Joined
Jan 18, 2011
Messages
2,876
Re: Acid washing growth off fiberglass bottom in Fresh water????

The On-Off (Mary Kate) recommends not to put on aluminum. Get yourself the blue lid bottle of TY-D-Bowl cleaner. Mix it with 40% of hydrogen peroxide.
 

moosehead

Chief Petty Officer
Joined
May 29, 2012
Messages
437
Re: Acid washing growth off fiberglass bottom in Fresh water????

MSDS review of some mildly acidic cleaners popular for hulls showed the following in ascending order of acidic strength:

Starbrite: 5-10% Oxalic Acid

Bar Keeper's Friend: 5-10% Oxalic Acid

Sno Bowl: 10-20% Hydrochloric Acid

Mary Kate On Off Hull Cleaner: 20-25% Hydrochloric + 5-10% Phosphoric, 1-5% Oxalic
 

crabby captain john

Lieutenant Commander
Joined
Aug 6, 2011
Messages
1,823
Re: Acid washing growth off fiberglass bottom in Fresh water????

On/Off about $20 a qt,,, muriatic acid about $5 per gallon....
 

badcarma58

Seaman Apprentice
Joined
Nov 15, 2010
Messages
33
Re: Acid washing growth off fiberglass bottom in Fresh water????

I tried the toilet bowl cleaner mixed with hydrogen peroxide. It didn't do anything.

So, I sprayed the muriatic acid onto the hull. Worked great. Had to scrub a little. Boat is on trailer, so I tried to spray water on it as much as possible to wash acid away. I need to raise boat and do rest of hull this weekend. We'll see if I damaged the trailer at all.

Thanks for ideas.
 

Mason78

Petty Officer 1st Class
Joined
Sep 20, 2011
Messages
224
Re: Acid washing growth off fiberglass bottom in Fresh water????

I have had success with the Muriatic acid. Its nasty stuff though! make sure you protect your eyes.
 
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