Engine bottom paint -

jstates · Posted: Thu Jul 05, 2007 10:10 pm Post subject: Engine bottom paint -

During last pull out I noticed increased numbers of marine life attached to lower aspect of Honda 40 mounts. I had been paying attention to hull bottom paint that was in relatively good condition. After trying to remove the shells, talking to local Pickering Marine - about the correct paint he said we needed to strip the lower metal, then apply primer and correct bottom paint for metal. [which we purchased] No problem with the latter two. - But once I strip or sand the the shells off I will have bare aluminum. How do I prepare the metal for the bottom paint primer and bottom paint. -

I have kept the usual hull bottom paint away from the motor mount and the zincs and understand need to be sure zincs have good contact with engine mount.

I did search our site under bottom paint and engine paint [lots of entries] and remember seeing one recent post about painting engines but can't seem to locate it.

I am sure this may be discussed somewhere and would appreciate a link and or suggestions about keeping the engine mount clean - The CDory is in Salt water most of the year

Thanks

Jim

Alok · Posted: Thu Jul 05, 2007 11:07 pm Post subject:

West Marine carries both primer and anti-fouling paint for aluminum. The spray type is quite easy to apply.

thataway · Posted: Thu Jul 05, 2007 11:26 pm Post subject:

Prep the alumium by thorough cleaning (sandblasting or sanding)--cleaning with solvent and coating with Alodine. The Alodine has to be removed (it is more of an etching/conversion to oxide) and then paint with two part epoxy Strontium-ChromatePrimer. After that, you can put on the non copper bottom paint designed for alumium. You have to keep the copper of the "usual" bottom paint away from the alumium. Some bottom paints have copper thiocyanate and have been used on Alumium as well as on boat bottoms. Vivid by Pettit is such a paint. Also West Marine makes a copper thiocyanate spray for alumium. There is also Pettit's Alumaspray which contains zinc pyrithione as a biocide.

Doryman · Posted: Thu Jul 05, 2007 11:46 pm Post subject: Re: Engine bottom paint -

jstates · Posted: Fri Jul 06, 2007 11:51 am Post subject: Engine bottom paint -

Thanks for the information. The Science of all this is fascinating.

Does anyone have a good sander for irregular surfaces like the motor mount- there were several mentioned under fiberglass repair for flat surfaces.?

Thanks again

Jim

Sea Wolf · Posted: Fri Jul 06, 2007 11:59 am Post subject: Re: Engine bottom paint -

thataway · Posted: Fri Jul 06, 2007 3:01 pm Post subject:

Small sandblasters are relitatively inexpensive. Basically a hopper and gun or even a single unit which holds a couple of pounds of sand.--assuming that you have the air compresser (see my previous posts about the advantages of air tools. As Joe notes, you have to mask the fiberglass (never sand blast fiberglass boat bottoms). Several layers of good masking tape and heavy paper suffices for the masking.

Use commercial grade sand (dont' go to the beach!). Have the shop vac ready and you can basically use plastic to enclose the small area you are working in--and capture the used sand/paint. You can get a small sand blaster for $60 to $100.

There are a couple of sanders which are nice for irregular surfaces--These are called "detail sanders" I have the Ryobi detail sander , which is limited, and I have a Dremel 6001 Contour detail sander, which is more helpful. The best is Fein the multitasker--similar to the Ryobi but much more versitile--and expensive. The Fein also works as a oscullating saw, scraper etc--lots of functions. Of course the Standard Dremel tool (or larger Rotozip, with adaptors) is always useful when working on surfaces like this. You can get "abrasive pads, and wheels" which will strip paint, and not damage the metal.

I would start by masking right next to the metal (probably use duct tape to protect if you are using any power tools). Start with a good small scraper or scraping blade. Scrap all that you can off. You can use emery cloth for metal--it is much more durable than sandpaper. It can be afixed (glued or stapled) to pieces of wood, to get into corners.

I have used both the single part spray cans, and the two part epoxy. My experience is that the two part epoxy primer is much harder. (Recently I did some corrosion work--and used mostly JB weld--for this , where there was minimal abrasion of the alumium on the motor, I used the spray can, but all of the crevices were bonded with the JB weld, epoxy.