Bottom paint recommendation

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Bottom paint recommendation

Postby kimbo » Fri Oct 13, 2017 9:09 am


Recently acquired a beautiful M-39 and need advice. From the attached photo, what is the recommended procedure and estimated cost for painting the bottom of this 39.



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Re: Bottom paint recommendation

Postby bcassedy » Fri Oct 13, 2017 12:02 pm


First, welcome the forum!!! :-)

Unsure if your pic's "light area" is actually bare aluminum or a previously painted surface. If bare aluminum, you're going to need to scrape the entire surface to remove any loose paint AND THEN sand all exposed aluminum. This may be more effort as compared to getting someone to (sand) blast the bottom down to bare aluminum***. Cost - I paid about 350.00 to have mine done several years ago. Shop around!
*** You MUST!!! apply at least 1 coat of a 2 part epoxy primer (Interlux's Interprotect 2000E is what I recommend) IMMEDIATELY. Newly exposed bare aluminum will quickly develop an oxidation layer to protect itself. That oxidation layer will cause failure of applied paint to adhere to the hull. One coat is all you need immediately. (See below if you have pitting in the hull). After that 1st coat <and pit filling, if needed> you'll want to apply 1 or 2 additional coats. I say this because, down the line, you'll want to apply another coat or 2 of bottom paint. There can be a time lapse between coat 1 and 2nd coat of the 2 part epoxy primer. With the surface having 2-3 coats of epoxy primer applied and in good condition, you won't have to worry about sand blasting again.

After the 1st primer coat - if the bottom has any pitting, now is the time to fill in those pits (Process recommended by forum "old hand" FastJeff). My recommendation is a product called PC-11 which is a 2 part waterproof epoxy (fairing material) that wears like iron. Mix only enough that you can readily/efficiently apply with a heavy duty plastic paint scraper. I'd shy away from metal scrapers. They could scour / gouge thru the 1st primer coat. Smooth the PC-11 as best you can. Once it's cured, it's a bear to sand down (but can and should be done). After pits filled apply the 1-2 added coats of 2 part epoxy primer.
--> I would recommend different colors for the epoxy primer- start with gray, 2nd - white, 3rd - gray. This way you'll be able to see any spots you missed AND when getting ready to reapply bottom paint, you'll be able to see just how badly the bottom paint has worn down (ie. you see white - 1st coat of bottom paint - you should apply 2 coats of bottom paint after prepping hull, all you see is black (or mostly black <or whatever color your final coat will be>) then the bottom paint's holding up pretty good. Maybe a touch up or maybe just 1 coat needed.

Bottom paint -
NOTE - some bottom paints require the initial application within a certain time frame after the last primer coat's application.

I just repainted the bottom of Sunset Seeker with Interlux's Micron CF. I painted 2 coats - 1st white, 2nd black. Doing so ensured the final coat was thoroughly applied. The white coat pretty much assured I covered the previously applied bottom paint.
IMPORTANT - under no circumstances should you use any paint containing copper!!! Doing so will cause deterioration (corrosion) of the hull. Yes, the Interprotect affords some protection, but do you really want to chance it. And Interlux's non copper paints are quite good. There are a number of other copper-free brands out there and I hope that other forum members will add their 2 cents pro and con.

Cost and coverage - somewhere on the web there are calculations for determining the surface area of a boat's bottom and the amount of paint needed. Here's one: ... e&ie=UTF-8
If you're a very good painter, you can rely on these calculations. If you're like me, you might want to add an additional quart of bottom paint per coat. It's lousy to be painting and realize you're going to come up short. Then it's setting things aside, running somewhere to pick up a (expensively priced!) quart. I have found the best pricing for what I use to be Wholesale Marine. But I urge you to do some research before buying. You never know when you might run across a deal.

Last edited by bcassedy on Mon Apr 16, 2018 3:57 pm, edited 4 times in total.
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Re: Bottom paint recommendation

Postby barkleydave » Fri Oct 13, 2017 1:22 pm

Painting an aluminum hull is NOT straight forward. You must follow specific preparation and special primers. If unfamiliar with the process Interlux has detailed application guides on line. Your cost could go as high as 3000k for a proper application. Welcome to boating in a Big M.

Improper methods and prep can destroy a hull very quickly. I use to do the work myself but no being older and due to EPA regulations regarding paint dust etc. I now leave it up to a boatyard that does it correctly. I cringe every few years but my hull is in perfect condition. I am in the water 12 months so I do it every 4th season.
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Re: Bottom paint recommendation

Postby jralbert » Fri Oct 13, 2017 1:41 pm

Just want to restate and emphasize what Mr Cassedy wrote above: After sanding or sandblasting initially, as he noted, first primer coat must go on within a few hours to prevent oxidation. That oxidation process is aluminum's way of putting on a protective skin to keep it from rusting. Once your primer coat is on, you can relax and follow his detailed plan. If you want to add more primer coats, the timetable is no longer critical. You will, of course, immediately notice more peppy response from your boat when the work is completed. You will make up some of the cost of painting in lower fuel consumption, Good luck with the project
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Re: Bottom paint recommendation

Postby Maestro » Mon Oct 16, 2017 9:11 pm

I will echo what others have said regarding the process and getting primer on quickly after exposing the aluminum. For a 39 a second person to help prime would be good.

I have been successful with Interprotect 2000e primer and used Sea Hawk Mission Bay as the anti fouling.

Used Micron CF initially and was not happy with the longevity. Sea Hawk has held up better for me.
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Re: Bottom paint recommendation

Postby ericinga » Tue Oct 17, 2017 7:01 pm

Paint selection depends location and water conditions. Check with local boat yards and find out which paint brand performs best in your area. You should call the paint companies. They are aware of local variations in paint performance. I found them very helpful. The local yards on Lake Lanier say Petit brand products hold up better than Interlux on the lake. I chose to use Interlux this time around. The last paint applied to our boat was a Seahawk epoxy primer and bottom paint. The paint performed well. Our boat will be stripped and painted in a week or so. I don't have time and will be paying someone for the first time.

A note on oxidation: If you do strip the boat and leave the aluminum bare for more than three - four hours, an etching solution of muriatic acid can be applied to etch the aluminum and prep for paint.

Pay attention to inter-coat times. Many primers have specific time or tackiness parameters between the prime and paint coats. This is true with SeaHawk epoxy primer.
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Re: Bottom paint recommendation

Postby jralbert » Tue Oct 17, 2017 9:20 pm

I'd like to offer this suggestion again. Instead of guessing and trading hearsay about which paint performs best why don't some of you undertake an actual side by side comparison put your favored paint alongside another brand and see how they fare again slime and critters after period of time at your dock. Post the results. I did that in cooperation with another forum member more than 10 yrs ago (at that time, Interlux easily beat out what had been my favored brand ZO No Foul) so it's time for a repeat but this time I don;t have a dock or a boat. It's up to you. No need for all to buy a quart to test. You could xchange small quantities for just postage. It'll take a few summer months to gather the data, but at the end you'll be informed. Just offering an idea.
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Re: Bottom paint recommendation

Postby Tedstriker22 » Wed Oct 25, 2017 7:53 pm

I used to use Trilux 33. Worked ok but turned from black to grey once it got wet. This year I used Seahawk brand paint for aluminum. Works great and stayed a nice dark black.
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Re: Bottom paint recommendation

Postby TinChips » Fri Oct 27, 2017 7:47 am

I have moved away from Trilux 33 and went with Alumipaint AF from Totalboat. It covers better and is much cheaper. Since it is compatible paint system, I didn't have to sand to bare metal. They even gave me free coveralls and a paint tray with my order.
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Re: Bottom paint recommendation

Postby Jcbwell » Mon Nov 13, 2017 8:26 am

Having my 37' done now, at Huckins Yacht Corp in JAX FL. Needed sandblasting, due to flaking. Huckins had best rep, & gives written quotes.

Sandblasting, 2 coats self-etch primer, 2 coats hi-build epoxy. 2 coats anti-fouling paints, all Petit non-copper.

Est is about $5300 total (ouch) but we're love-aboards, so want a good finished result.

Hope this helps.
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