What's this?!!

[jwatson]

Got myself a merc 4hp to refurb and use as an auxillary. Spotted this beneath the cav plate and have no idea what it's for!!

[Dry Run]

Looks like an anode?

[m chappelow]

Its called a Sacrificial Anode ,
over time it will corrode away & need replacing hence "Sacrificial " it helps stop galvanic corrosion of the engine parts especially the aluminium .

[jwatson]

Blimey!!! How does that work then?!

[rigi36]

It corrodes and your engine doesn't

[jwatson]

That's pretty clever! Looks like it should have had one for much longer :oS

[Ribochet]

Originally Posted by rigi36

It corrodes and your engine doesn't

Not if it is made of zinc

Originally Posted by jwatson

Looks like it should have had one for much longer

I wonder why

[uncle al]

it is an anode and will require replacing in the future, so once it has only about a third left, then is the time to replace it. team tip before fitting a new one make sure that there is a good earth connection, and using a marine grease put a little on the bolt/screw so that when it needs replacing in the future it will take just a couple of minites. NEVER wire brush it to clean it, NEVER paint or put anything on it. If you ignore the nevers the OBM will probaly corrod but the anode will look nice.

[gary222]

Oooh didn't know about the wire brush bit, why is that ? Are you not exposing more of the metal by doing that?

[uncle al]

you dont wire brush it because, it will corrode quicker as it will now be dis-similar metal, just dont go down that road, as its fraught with problems.

[Nick Hearne]

Originally Posted by uncle al

you dont wire brush it because, it will corrode quicker as it will now be dis-similar metal, just dont go down that road, as its fraught with problems.

Wont be doing that again then!