Removing Bottom Paint

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
ChrisL
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Removing Bottom Paint

Postby ChrisL » Tue Sep 14, 2021 8:32 pm

I have a c.2006 DAUNTLESS [of unspecified length] that has one coat of bottom paint. Bottom paint was applied in 2020 over shiny gel coat. Now the bottom paint is flaking off in spots. [The flaking-off of bottom paint] is great because this DAUNTLESS is a trailered boat.

I am not sure what solvents will attack gelcoat. I was thinking to use a product called CITRISTRIP [to remove the bottom paint].

Q1: what is the easiest method to remove the bottom paint while doing the minimal damage to the gel coat?

Q2: how about a solvent like lacquer thinner or acetone?

jimh
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Re: Removing Bottom Paint

Postby jimh » Wed Sep 15, 2021 7:56 am

ChrisL wrote:Q1: what is the easiest method to remove the bottom paint while doing the minimal damage to the gel coat?

The easiest method for removing bottom paint is to use your check book, and hire the work to be done.

A method using air-blasting with mild abrasive powder, often called "soda-blasting", can remove bottom paint from a hull without causing harm to the gel coat. The gel coat layer will be abraded somewhat by the soda blasting and will no longer have a gloss finish, but there should be no chemical reaction.

jimh
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Re: Removing Bottom Paint

Postby jimh » Wed Sep 15, 2021 8:01 am

ChrisL wrote:Q2: how about [using] a solvent like lacquer thinner or acetone [to remove bottom paint]?

While acetone may dissolve the bottom paint and allow you to wipe away the paint, it will also affect the gel coat. I would be very cautious using acetone; you may end up impregnating the bottom paint into the gel coat more deeply that the original paint was.

A good approach to test any method of bottom paint removal is to apply the method to a small and inconspicuous area of the hull to see how effective the method will be at removing the bottom paint, before committing to using the method on the entire hull.

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Phil T
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Re: Removing Bottom Paint

Postby Phil T » Wed Sep 15, 2021 8:24 am

While a majority of owners recommend paying a professional to soda or shell blast the paint off, there are a few non-toxic removal products.

I recently used Smart Strip to remove very old bottom paint with good results. It is still a LOT of work.

I did a test on a small area and found applying a thick thick layer and letting it sit for 24-hours was the most effective. It took three applications. The next step to wash residue, followed by wet sanding and polishing.

To do a complete 17-foot hull I estimate would take about 40-hours of work and require as much as three gallons of SmartStrip.

Smart Strip is available at Sherwin Williams paint stores, online, Amazon. Best price for 1-gallon was at Lowes for $52.98.
https://www.lowes.com/pd/Dumond-Smart-Strip/1000615057

Note - Some components of bottom paint are highly toxic. Proper clothing and protection is required. Proper collection and disposal of the residue and removed paint is necessary. Mechanical removal (sanding) is NOT recommended.
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ChrisL
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Re: Removing Bottom Paint

Postby ChrisL » Wed Sep 15, 2021 1:07 pm

bottomPaint1.jpg
Fig. 1. An image of a hull bottom that was posted with no explanation or caption or reference in the text.
bottomPaint1.jpg (53.84 KiB) Viewed 951 times


jimh wrote:A method using air-blasting with mild abrasive powder, often called "soda-blasting", can remove bottom paint from a hull without [img]causing harm to the gel coat. The gel coat layer will be abraded somewhat by the soda blasting and will no longer have a gloss finish, but there should be no chemical reaction.


Q3: [after bottom paint has been removed using soda blasting, can you buff the gelcoat back to a shine?

Q4: or will the gel coat first require sanding?

In the near future someone will call me to discuss soda blasting.

In the long ago past I used a pressure washer and sand blasted a 1970s Nauset. That worked great, but the method left a very rough finish.

SInce my Dauntless is going to live on a trailer, I see no reason to have it painted.

Q5: [can] Dumond Peel Away [do a good job to remove bottom paint]?

I called them and they said their stripper works great for gel coat.

Thanks for all the advice.
Chris

jimh
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Re: Removing Bottom Paint

Postby jimh » Wed Sep 15, 2021 1:45 pm

Another outcome of removal of bottom paint (which generally inhibits marine plant growth) when working on the boat on a driveway or lawn is inhibited growth of grass in the general work area.

jimh
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Re: Removing Bottom Paint

Postby jimh » Wed Sep 15, 2021 1:53 pm

If the bottom paint is very poorly bonded to the underlying glossy gel coat layer, try experimenting with a plastic putty knife as a tool for removing the paint. Sharpen the edge of the plastic putty knife. See if you can remove the loose paint in an effective manner.

I had another Boston Whaler boat with poorly-adhered bottom paint. I was able to remove all the bottom paint from the transom by using a putty knife with a sharpened edge. In this method you must be very careful in using the tool to not create scratch lines. Minor marks in the gel coat can be sanded out and polished to become invisible. The method was effective, but I gave up on doing the whole hull (a 20-footer) because it was too labor intensive.

Running the boat at planing speed in the water for a few years will remove loose bottom paint without any special effort.

roadpupp
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Re: Removing Bottom Paint

Postby roadpupp » Fri Sep 17, 2021 11:04 am

I used Dumond Peel Away. They have one formula that is safe for [that is, does not remove] barrier coat and another formula that is made to take off barrier coat. Neither formula of Dumond Peel Away should damage gel coat.

To strip, sand to white gelcoat, paint [three coats of] epoxy barrier [paint], and [apply] bottom paint on a 21-feet Ventura took me 60-hours of work.

Jefecinco
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Re: Removing Bottom Paint

Postby Jefecinco » Sat Sep 18, 2021 9:59 am

Last night watching an archived "This Old House" video episode I saw an interesting method to remove char and soot covered wood from a fire damaged home under restoration. It immediately made me wonder if similar technology would work as well for removing bottom paint from gel coat.

The method involved blasting dry ice pellets at the char and soot which removed it with no apparent damage to the good wood beneath. It was interesting to hear the very brief explanation of how the process works. When the pellets are sprayed at a high pressure they sublimate into carbon dioxide gas upon reaching the target surface.

The work was done by a professional company.
Butch

ChrisL
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Re: Removing Bottom Paint

Postby ChrisL » Tue Sep 21, 2021 9:41 pm

After receiving a quote of $1,700 for soda blasting, I decided to buy a tub of Peel Away.

Peel Away worked amazingly well. A quick buff with a 3M cleaner wax was all that was needed to restore the factory shine.

IMG_1378.jpeg
Fig. 1. an area of bottom paint removed using Peel Away.
IMG_1378.jpeg (169.18 KiB) Viewed 784 times