painting lower unit question

[2cycle]

Hello, I'm in the process of restoring my Merc 1500 with new paint and decals. I'm going to be doing the lower unit and midsection too. There are several areas that are pitted on the surface even after sanding, so I'm going to need to use some filler to even it out.

So...can you use Bondo on metal below the water line effectively, and it not what should I use?

Also, what type of primer should I use and where can it be found? Any other tips welcome as well. Thanks for the replies!

 

[Frank Acampora]

Re: painting lower unit question

No, don't use Bondo. It's no good in the water. even coated with paint. Try some type of epoxy filler. As for primer, I don't knoe about Merc but other brands used a zinc chromate primer You should be able to find it on line but it will be expensive-- probably 7 bucks for a spray can.

 

[Chris1956]

Re: painting lower unit question

2-cycle, You may use a marine polyester (or epoxy) putty on the pits. Use the Zinc Chromate primer. The orig. Merc paint was Phantom Black Lacquer. You can buy this in a spray can, or use some standard black lacquer.

 

[tmh]

Re: painting lower unit question

Rather than start another lower unit painting thread, I'll ask another detail here and follow along. When painting the lower unit of a I/O does one have to be particularily careful not to spray into certain areas? By this i mean there are moving parts and I wouldn't want the paint to "bind" these parts so they no longer moved freely. Is this a concern or does on just paint it all? Thx.

 

[stevieray]

Re: painting lower unit question

tmh - mask off any exposed stainless steel items (nut & bolt heads, zerks, the lines to the trim cyls, prop shaft) and all the anodes. If you take off the anodes, mask off the mating surfaces & screw threads where they attach. Everything else can be painted.

 

[Chris1956]

Re: painting lower unit question

tmh, You can put a bit of grease on the bolts and zerks, and the paint will not stick. Remove or mask the zinc anodes.

 

[tmh]

Re: painting lower unit question

OK, thanks. What's a "zerk"? Sounds like a Dr. Suess word.

 

[Chris1956]

Re: painting lower unit question

tmh, A "zerk" is the common name for a grease fitting, that a grease gun can pump grease into.

 

[Saskatoon2005]

Re: painting lower unit question

There is a liquid metal filler you can buy at auto stores. I think it is made by JB Weld. With these fillers, you can use the zinc chromate primer on them and then paint them just like metal. Works great.

One is liquid metal, and the other is liquid aluminum, either one will work.

 

[jy118lfd]

Re: painting lower unit question

You must treat the pits with acid or nothing will stick to them. The salt will not come out with just sanding. There is another thread on painting an outdrive on the sterndrive forum but I can't seem to find it with this D#@# new search.

 

[tmh]

Re: painting lower unit question

Great thread, thanks for all the great info! I was totally intimidated by the prospect of painting my outdrive this spring and was going to have it done for me. Now it doesn't seem so difficult. Mine is a 20 yr old alpha one and I really don't care much if it looks great, I just want it protected. Yeah, all else being equal i'd like it to look decent also, but that;s secondary.

Cleaning (etching) with acid isn't as bad as it sounds and I've used JB Weld 'liquid metal" on the kids gokart and it's not too tough. I just wonder if I NEED to fill in small pits or if that's more for looks than function? Can I just do the acid etching then paint the pits as is?

 

[stevieray]

Re: painting lower unit question

Depends on how small the pits are. If you can "fill" them with the zinc chromate primer to the point where you're satisfied with the looks, then you don't really need any other filler. I've seen them with literally chunks of metal missing & they performed fine. If you can apply the black lacquer carefully (thin coats - no runs or orange peel) you should be more than happy with the results.

 

[2cycle]

Re: painting lower unit question

Hey guys, thanks for the info. Another question, where are the zinc anodes on the lower unit? I'm baffled.

Also, re: zinc chromate primer, what is the reason for its use? Is it because of exposure to water, meaning can the cowl or anything above the waterline utilize standard automotive primer (I already primed the cowl with regular stuff)? Thanks for the help!

 

[wreckless]

Re: painting lower unit question

What type acid is used to clean the aluminum on lower unit?

 

[stevieray]

Re: painting lower unit question

2cycle & wreckless - here is "by the book" materials & procedure. Aluminum should be treated with the alumiprep (acid) and conversion coating (neutralizer) before priming with zinc chromate (which provides a chemical bond with the bare aluminum that no other primer can).

Refinishing procedure:

This procedure should be used in refinishing MerCruiser sterndrives and transom plates. This procedure will provide the most durable paint system available in the field. The listed materials should be purchased from a local DITZLER AUTOMOTIVE finish supply outlet. The minimum packaged quantity of each material shown is sufficient to refinish several sterndrives and transom assemblies.

1 QT. DX-533 Alumiprep #33 metal preparation
1 QT. DX-503 Alodine #1201 conversion coating
1 QT. DP-40 Non sanding Epoxy Primer zinc chromate primer
1 QT. DP-401 Catalyst for DP-40
1 QT. DAR-9000 Acrylic Enamel-black topcoat
1 Pt. DXR-80 Delthane Ultra-additive for acrylic enamel
1 QT. DTR-602 Acrylic Enamel Reducer-temperature range 70-90 degree F.

PROCEDURE:

1. Scuff sand to remove all blistered paint and roughen factory finish. Remove sanding dust.
2. Follow manufacturer's recommendations and instructions on the individual containers.
3. Apply DX-533 (Alumiprep #33) to clean and condition the aluminum.
4. Apply DX-503 (Alodine #1201) brush on chemical conversion coating for aluminum.
5. The DP-40 (Epoxy Chromate Primer) mixed with DP-401 Catalyst can now be applied. A .75 mil film build is recommended.
NOTE: Allow 30 minute induction period for permeation of the epoxy chromate primer and the catalyst prior to application.
6. The topcoat consists of DAR-9000 Acrylic Enamel Black and the DXR-80 Delthane Ultra additive, and DTR-602 Reducer. It is a polyurethane acrylic enamel system which provides fast drying, durability, high resistance to corrosion and good color and gloss retention.
7. The type of spray gun used will determine the proper reduction ratio IMPORTANT: DO NOT use any type of aerosol spray paints, as the paint will not properly adhere to the surface, nor will the coating be sufficiently thick to resist future paint blistering.
NOTE: DO NOT PAINT SACRIFICIAL ANODES.


Or you can use plain white vinegar for the acid, neutralize it with a baking soda/water solution & use spray bombs for zinc chromate & finish black lacquer. I have used this method with great success.

 

[2cycle]

Re: painting lower unit question

Stevieray,

Thanks! That is a great post that I'm sure will help a lot of folks. That gives a lot of direction.

 

[Gabby]

Re: painting lower unit question

Furthering this dicussion. My hull has A-F paint which I plan on removing. Previous owner also painted the lower unit with some sort of black anti fouling paint that covered the original beautiful gloss by Mercrusier. Anyway to get that off to repaint my lower unit or am I stuck with that matte black finish?

 

[Yacht Dr.]

Re: painting lower unit question

Yea..there is many ways to get AF paint off..

Resporator..gloves..Grinding suit .. some stripper..wire brush..flat blade screwdriver and anything you can think of to get in those hard to get places ..

Proper prep is the key after that.

YD

 

[stevieray]

Re: painting lower unit question

Yea..there is many ways to get AF paint off..

Resporator..gloves..Grinding suit .. some stripper..wire brush..flat blade screwdriver and anything you can think of to get in those hard to get places ..

Proper prep is the key after that.

YD

One other note - make sure any scraping tools you use are brass or aluminum (especially the wire brush). Very small steel particles tend to stick in the aluminum outdrive parts & will add to the corrosion problem later.