Outdrive anodes and the surface underneath (Volvo Penta DP290 series/DP-G)

[frazion]

So my outdrives are getting a sandback and paint. There is bare aluminium where its clear that a previous owner has sanded back and slapped on a coat of antifoul primer straight onto the aluminium. Thats another story and I've got plenty work to do to etch-prime etc etc etc.

But it got me wondering....when it comes to anodes, should the area underneath the anode be bare metal or is it presumed that the conductivity through the bolt hole is sufficient for that purpose? if so, why the required scrape back and clean of the mating surface for the circular prop anode?

 

[QBhoy]

Not sure about answering your question…but I remember picking away at the anti foul on my 290 and thinking it was bare metal underneath and that someone had sanded back…but turned out to be original VP paint…that happens to look very aluminium coloured

 

[frazion]

Thanks. That makes a lot of sense and does answer my question! Or at least confirm my thoughts. Still don’t quite get the whole bearing housing scrape back or perhaps it’s because that part is never painted so the instruction is to ensure it’s clean with there being no possible anti fouling.

 

[Momac]

There is original paint on my 290dp-e outdrives including the location where the anodes fit. The anodes definitely work with no issues .
This is from experience since 2014 with my present boat.

 

[Momac]

I though the fish might like to see green props this time

 

[frazion]

I though the fish might like to see green props this time
View attachment 133111

Awesome! Screw anti fouling, let’s visually psyche them out!
Maybe add purple yellow?

 

[Momac]

Awesome! Screw anti fouling, let’s visually psyche them out!
Maybe add purple yellow?

I had used paint on the props (from the same source as the fresh paint) at the previous lift out two years ago (although that paint was black) and that was very successful with negligible paint loss from the props . This was a remarkable result as all previous efforts has resulted in very little paint remaining on the props.

This time a light rub down without removing all of the previous paint was all of the preparation required. Then a fresh coat of the brush applied primer and the spray top coat.
The primer used is Hammerite Special Metals primer. This seems to be the significant ingredient.

The boat is on fresh water with very occasional salt water trips. We get a thin coat of limescale on the outdrives and props but that is not detrimental to performance. I did apply an antifoul suitable for aluminium on the skegs of the legs last time but it had the limescale on it just the same as the rest of the leg when the boat was lifted.
The colour of the paint is irrelevant and it is of course not visible now the boat is back in the water . The green paint was free issue via a friend. It's surplus stock but is good quality automotive spray can paint . I have a can in a more vibrant green for next time.