[w2much]

How often does this anode need replacement. Never messed with a lower unit . Manual says "moderate" difficuly in replacing.

[Vic.S]

It depends how much of the time it is immersed in seawater, but generally anodes are replaced when more than half corroded away.

It is not inside the gear case though is it. it is shown on the parts diagram but not how it it fixed
#51 in this diagram

[ezeke]

It is #52 in the diagram, connected to the underside of the bearing carrier by two screws.

When you reseal the the gearcase and have the carrier out, you replace the anode. Otherwise, you don't usually do them.

The other anodes need to be kept in perfect shape though because that one will have long ago failed.

[Vic.S]

Didn't see that ... only the next thing on the list! Seems pretty daft to have anode somewhere you cant check regularly. #51 is easy to check and renew though is it?

Still got the original anode from 1985 on my engine. Looks ok. Can't undo the screw now anyway.

[ezeke]

If the water that you run in is chemically neutral, you may never miss an anode.

The only way to check them is with an ohmmeter, Although when the zinc oxide turns the anode light gray to white its not working on that surface anymore.

[twostroke87]

I wouldn't mess with that anode unless you need to reseal your gearcase.

Take a test light, hook it up to the + side of the battery, and then poke all of your engine anodes with the test light, if the light comes on your anodes are properly grounded and you are good to go. Keep all of your easily accessible anodes in good condition and you'll be good to go.

If the light does not come on, then your anodes are not properly grounded and will not work properly. You need to check and find where it lost its ground and repair it, otherwise even with a new anode they will not work properly.

[w2much]

Thanks , I have changed my two exterior anodes, they were not that bad at all. Pricey little hunks of metal. Feel better having done them.