Best Prep/Primer/Paint combo to keep paint on LU?

[imq707s]

I've tried several different primers and epoxys, but I just can't seem to keep the coating on my lower unit. What am I doing wrong?

Here is what I tied the last time...it lasted for 4 80mph runs before it started ripping the primer off.

1. Sand gearcase down to bare aluminum with 80 grit paper.
2. Smooth out the nozecone epoxy.
3. Sand Epoxy down with 80 grit paper.
4. Spray a thin coat of that green self etching primer made for aluminum.
5. Spay a few coats coats of that rattle-can grey primer on the LU.

Done.


When it starts to peel off....it seems like some spots the epoxy starts to peel away from the aluminum, and other spots the primer starts to peel away from the epoxy.

What the best way to prep and paint a LU? I want to have the grey primered look...instead of a glossy black LU. Is it possible to do that and still keep the primer on the LU?

Thanks for the info guys.

[The Big Al]

Have it powder coated!

[David - WI]

5. Spay a few coats coats of that rattle-can grey primer on the LU.

Lacquer-based primers absorb water, swell up, and blister. You're not really even supposed to wet-sand them if you can help it... much less immerse them in water.

If wet sanding is preferred, allow sufficient time for moisture to evaporate. Avoid wet sanding lacquer type primer surfacer when possible.

Blistering

I think "rattle-can grey primer" is the problem. Anything in a spray can that says "primer-surfacer" or "sandable" is probably lacquer-based.

I would look for an epoxy (non-sanding) primer if you want it to look that way.

[tigweld]

I use a DuPont non corrosive epoxy primer, and Imron for finish.

[Bruster]

I've tried several different primers and epoxys, but I just can't seem to keep the coating on my lower unit. What am I doing wrong?

Here is what I tied the last time...it lasted for 4 80mph runs before it started ripping the primer off.

1. Sand gearcase down to bare aluminum with 80 grit paper.
2. Smooth out the nozecone epoxy.
3. Sand Epoxy down with 80 grit paper.
4. Spray a thin coat of that green self etching primer made for aluminum.
5. Spay a few coats coats of that rattle-can grey primer on the LU.

Done.



When it starts to peel off....it seems like some spots the epoxy starts to peel away from the aluminum, and other spots the primer starts to peel away from the epoxy.

What the best way to prep and paint a LU? I want to have the grey primered look...instead of a glossy black LU. Is it possible to do that and still keep the primer on the LU?

Thanks for the info guys.

I guess "done" is the optimal word here. You're done before you get in the water with that combo. If you want any chance of the paint sticking, you need to remove all of the stuff you have put on so far. Prep the surface with 120 grit. Prime with PPG DP epoxy primer Sand with fresh 600 wet and topcoat with PPG single stage "concept" Acrylic Urethane topcoat. If that still don't stick you didn't follow the instructions on the can. If you don't have the equipment to safely spray this paint, take it to a body shop. Most all use pretty much this system. Just tell 'em what you want. I've probably done at least a hundred lowers using this paint system and have never had any issues.
If you want the primer look just do the DP Primer in grey.

Powder coat is the wrong answer. You'll have to disassemble your lower to have it coated and when you scratch it you can't repair it. Just don't understand.......

[imq707s]

Will the epoxy primer stick to the epoxy that I've used to blend the nosecone to the LU? That's where I have most of the problems. Is there one brand of epoxy primer that is better than the rest as far as adhesion?

Thanks for the info guys.

[Bruster]

Will the epoxy primer stick to the epoxy that I've used to blend the nosecone to the LU? That's where I have most of the problems. Is there one brand of epoxy primer that is better than the rest as far as adhesion?

Thanks for the info guys.

Yep, It'll stick, if it's epoxy.

I think PPG DP is the standard everything else gets measured to.

[K-Dawg]

You can repair the powder the same way you would paint feather it and prime then top coat. But, I agree powder would likely get chipped up alot there. Anybody ever try a zinc rich primer? I know it works really well on aluminum. I don't know how well it would handle the speed though or, heat from the exhaust. Water based coatings are probable a waste of time for immersion service.

[kimswang]

Follow Brusters instruction, it works! Then three days after you have painted it with Imron (if you choose Imron) or concept, wet sand the gray topcoat with 600 paper and you have your primer look only smoother and lasting...

[A Fn Noob]

I painted the lower unit of an old 40hp, I stripped all the old paint and primer off, and used a can of white "appliance epoxy". Turned out perfect. You dont use primer with it, and you cant coat over it once it cures. I think it comes only in black and white, high gloss.

[mr_velocity]

I use a DuPont non corrosive epoxy primer, and Imron for finish.

Me too, although I start with the DuPont conversion coating. Been 10 years and no problems.

[JDChase]

Why don't you just sand it down and leave it? if you are looking for the raw aluminum look sand it with 120 dry, 180 dry, 400 wet then a red scotch brite pad, it will look great! spray it down with wd 40 occasionally. If you really want to paint it I will be glad to help, just let me know.

[JDChase]

PPG is a good epoxy. I use only SPI epoxies and primers on all my high-end rod builds, or anything for that matter. Southern Polyurethanes Inc. the manufacturer is located in Ga. their products far exceed any I have used, you can call 24-7-365 for tech support and if Barry doesn't answer he will get right back to you. he is the owner and the chemist who makes this stuff.

[talonkid]

Good rule of thumb - Epoxy bonds to everything, not everything bonds to epoxy. There are a few exceptions, but its a good basis.