Any tips on painting outboard motor lower unit ?

[rfuerst911sc]

Happy Easter guys/gals . It's warming up nicely here in Georgia mountains so getting the boat ready for maiden spring voyage . I have a 1986 Mercury 25 hp outboard with a lower unit that has seen better beauty days 😁 . The paint has pitting and general rough feel to it . So today pulling out the sanding tools .

My plan is to gently remove paint/primer layer with minimal removal of base aluminum . Not looking for show car quality , just want it to look good . Once I get everything smooth and clean can I use a Rust-oleum primer ? I will build several layers and sand to help level . Then is Rust-oleum gloss black an acceptable top coat ? My use is fresh water only and the boat is trailered so no extended storage in the water .

Any suggestions on primer or paint are welcome , just trying to clean up the old gal and protect the aluminum. Thanks

[Joe Bob]

Wouldn't hurt, you also can call the manufacturer and ask what they use/recommend. They be in Fond du Lac WI, dontcha know?

Remember to service the water pump impeller...

[VINMAN]

I use zinc-chromate primer. ( it's that greenish color.) It's nade for aluminum. Then just a standard outboard paint. But i think any high quality auto paint would work in your case.

[drcoastline]

Originally Posted by rfuerst911sc

Happy Easter guys/gals . It's warming up nicely here in Georgia mountains so getting the boat ready for maiden spring voyage . I have a 1986 Mercury 25 hp outboard with a lower unit that has seen better beauty days �� . The paint has pitting and general rough feel to it . So today pulling out the sanding tools .

My plan is to gently remove paint/primer layer with minimal removal of base aluminum . Not looking for show car quality , just want it to look good . Once I get everything smooth and clean can I use a Rust-oleum primer ? I will build several layers and sand to help level . Then is Rust-oleum gloss black an acceptable top coat ? My use is fresh water only and the boat is trailered so no extended storage in the water .

Any suggestions on primer or paint are welcome , just trying to clean up the old gal and protect the aluminum. Thanks

Happy Easter,

The lower unit is aluminum so some extra steps need to be taken. Aluminum begins to oxidize almost immediately when it come in contact with air/oxygen so adhesion can be a problem.

If your paint is intact leave it, you will never obtain the same level of prep as the factory. Lightly scuff and you can apply your new paint over the base paint.

Where your aluminum is exposed you have two options.

1. Get a can of zinc chromate (Aluminum primer) available at most marine supply stores. Wire brush the area to clean the oxidation, you want the aluminum shinny, immediately spray the chromate over the area to seal the aluminum, this will minimize oxidation. Let tack and apply two or three light coats allowing to tack between coats. Let tack then apply to or three light coats of regular primer allowing to tack between coats. You can then spray your top coat following the same procedure. Allow to tack between coats.

2. Get some marine epoxy- wire brush to shinny as above. put on some rubber gloves, mix epoxy get a piece of 100 grit sandpaper. Use a disposable chip brush and paint some epoxy on the exposed surface. Rub the epoxy into the aluminum with the sandpaper. This process will scuff the aluminum epoxying raw aluminum while simultaneously applying the epoxy. The theory is air will not touch the raw aluminum thereby reducing the chance of oxidation. Allow the epoxy to thoroughly cure, scuff the epoxy prime and paint.

Rustoleum will work just fine. I personally like epoxy paint. Many paint jobbers will now mix you a two part paint in a spray bomb. The epoxy paint is more durable then the Rustoleum. But if you don't mind a little maintenance and stay on the exposed areas, leading edge of the lower unit, fin mostly, brush or roll on a little Rustoleum that will be just fine.

[Joe Bob]

Sacrificial anodes also help. Wear item like brake pads.

[rfuerst911sc]

As always great advice from the Pelican community ! When I purchased the new to me outboard last year I changed the impeller as part of my baseline maintenance so good to go there . Yesterday I purchased a new sacrificial anode that will be installed after repaint . I will use the old anode as my " masking tool " to keep the mounting area free of primer and paint . I believe the anode works best when making contact with the base metal .

[VINMAN]

Yep, you definitely want the anode to have good contact. Normally, the mounting bolt does the job. My Yamahas have one on the cavitation plate, and another on the transom brackets.

I first repainted mine with Duplicolor touch up paint. Found a Hyundai color that matched the Yamaha color. When I did it again, I bead blasted them, then sprayed them with Crossfire auto paint with a gun.


.

[rfuerst911sc]

On this outboard the anode is a 3 5/8 " round disc with a fin on it . It mounts under the cavitation plate . By using the old anode as a masking tool the anode will have contact of the round disc and the bolt . It probably isn't even needed for freshwater but it's a while I am in there item .

I need to find some zinc chromate primer and buy whatever gloss black I decide to use . Rattle can will be fine .

[rfuerst911sc]

Yesterday I found locally a rattle can of chromate primer and black gloss auto paint . I hope to get it done this week .

[drcoastline]

Originally Posted by rfuerst911sc

On this outboard the anode is a 3 5/8 " round disc with a fin on it . It mounts under the cavitation plate . By using the old anode as a masking tool the anode will have contact of the round disc and the bolt . It probably isn't even needed for freshwater but it's a while I am in there item .

I need to find some zinc chromate primer and buy whatever gloss black I decide to use . Rattle can will be fine .

Freshwater still conducts electricity, not as efficiently as saltwater so an anode should still be used. If you are docked and a power supply is in the water and has a bad ground the electricity will find the easiest route you don't want it to be your boat.

[drcoastline]

FYI to my post above regarding the Rustoleum, you can make the Rustoluem more abrasion and chemical resistant gas, oil, etc. by adding hardener. Most hardware stores have small containers of hardener in the paint section 8/1 mix will chemically cure the paint vs, air dry. It's not necessary but adds a little extra protection.

The hardener will also allow you to wet sand and polish the Rustoleum (Enamel) should you desire. Probably not necessary for this project but maybe some other?

[Eric Hahl]

Por-15

[rfuerst911sc]

And done �� . Sanded the lower unit this morning , cleaned with compressed air and wiped it down with paint prep rag . Shot 3 coats of the zinc chromate primer allowing 5 minutes between coats . Let that dry for three hours in the sun .

Grabbed some 400 sandpaper and gave a light scuff . Wiped with rag and spray bombed the auto black . Came out fine with a few light runs . It's good enough for this year , maybe this coming winter I will sand and hit it again . No pics sorry it's just a black outboard ��. Appreciate the tips/advice given . Time to get her in the water !

[Bob Kontak]

Originally Posted by rfuerst911sc

It's good enough for this year , maybe this coming winter I will sand and hit it again .

Good deal. You will know how well you did this fall.

Note that small paint runs may promote unfavorable yaw. Don't run it over 50 knots until satisfied it's safe.

[rfuerst911sc]

Haha that's funny 😁 . To get 50 knots I think I would have to drop it from a C130 .

[Bob Kontak]

Originally Posted by rfuerst911sc

Haha that's funny 😁 . To get 50 knots I think I would have to drop it from a C130 .

You never know. You may happen upon a long downhill run.

Have fun and all the best!