Re-assembling drive unit, paint at the connection point?

[Gunn]

I removed one of my Alpha I Gen II stern drive units this past weekend and unbolted the two halves to replace the water pump. I had some corrosion issues bubbling up the paint and got it all scraped and sanded back to nice aluminum.

I noticed that at the junction between the two halves, there was paint there. Paint on the interior of the lower portion also. Since there is no gasket that goes between these two halves, I'm wondering...do I paint this surface area where the two halves join to protect them, or....do I NOT paint them so that there is an aluminum-to-aluminum connection between the two halves? I'm thinking the latter, so that there is complete "circuit" for the anodes to do their job. Maybe the existing paint at this joint was why I have the corrosion issues in the first place??

Any advice would be appreciated!

Tom

 

[plumbhappy]

Tom, what did you decide to do? I'm re-finishing my drives and I have been considering what to do about painting the matting surfaces. I also stripped my drive to bare alum and have read about using Alodine to prep the drive. Have you done this? What did you use to prime the drive?

Rob

 

[speakrdude]

In my experience, If you paint those surfaces, paint them very lightly. If you paint too much, the quad ring won't seal.

 

[Gunn]

Rob,

I ended up not painting the mating surface. I kind of forgot all about it, but after this season, it all looks great.

As far as primer, I can get you specifics but it was just a couple rattle cans of a green primer specifically for Mercruiser outdrives and aluminum.

Tom

 

[plumbhappy]

Thanks

I decided to use Interlux Primocon to prime the bare aluminum. I have also decided to primed the surfaces between the drives, but not paint this area. The Primocon contains aluminum so it should complete the "circuit" and maintain an alum to alum connection.

 

[dicor]

When you apply the Primcon to bare aluminum you must apply it within 30 minutes after sanding it. The reason being, aluminum oxidizes very quickly and will prevent the Primcon from adhereing correctly. I did my Bravo3 this winter, as a matter of fact I'm still working on it and in many places I took it down to the bare metal, after I completed all the sanding I began priming and one section at a time I lightly re-sanded right before applying it to remove the oxidation. Make sure you let the Primcon dry between coats (very important).
What finish coat are you using? I used Pacifico Plus we have a issue with barnacles here. Three coats of Primcon three coats of Pacifica Plus.
All the above info was obtained from Interlux support tech.

 

[plumbhappy]

Thanks for the info.

I did prime directly after sanding, more by accident then anything. I'm planning on three coats of primer and at least two coats of trilux 33. Not sure how long it'll last.