Corrosion problem - experience / thoughts please

[trying]

Posting this on behalf of a friend...

As you will see from the picture a hole has appeared in the top face of the transom shield (Mercruiser Alpha drive c.1994)...this is approximately 3" above the waterline...

His intitial thoughts, and mine too were galvanic corrosion but its not in the water?....

Anodes replaced annually. The trim tab anode on that drive is wearing a bit more than the one on the other drive...

Any similar experiences / comments would be greatfully received...

 

[carlton]

It seems a bit weird that that hole should appear above the waterline?

Hopefully our resident galvanic corrosion expert VicS will be along shortly with some suggestions...

 

[lovezoo]

Is there not a bearing in there? It might be above the waterline, but it will get wet. There is supposed to be a wire that connects the leg to the shield - is that still there?

 

[macnorton]

is it man made.

To replace the top seal/ bearing on those legs you need to remove the transom shield (after removing/engine leg) or make a hole to get at the top nut, could that explain it?

 

[paultallett]

To replace the top seal/ bearing on those legs you need to remove the transom shield (after removing/engine leg) or make a hole to get at the top nut, could that explain it?

My thoughts too. Maybe they had a steering seal leak and instead of doing it the engine removal way, decided to put a hole in the top of the transom shield?? Then mackled the hole back up with a bit of filler or something as it's above the water line?? Finally it's fallen out??

Just a thought.

 

[trying]

Lovezoo.... yes the top pivot is in there (bearing and top nut)...it'll need sorting out when the transom shield is replaced, his main concern is making sure that the cause is found and sorted out so as not to get a hole in the replacement transom shield!! The continuity wire is present between the steering arm and the transom shield and the ones outside were present/connected when the boat was out of the water last year for service etc...

Macnorton / Paultallett....
Not being my boat I'd not looked closely enough before to see if a hole had been made and filled but I'll pass the suggestion and see if he had noticed anything there on the transom shield before the hole appeared....

thanks for the input so far...

 

[VicS]

It seems a bit weird that that hole should appear above the waterline?

Hopefully our resident galvanic corrosion expert VicS will be along shortly with some suggestions...

Mercruisers and transom shields not my territory. I don't really know what I am looking at.

 

[GrahamHR]

It probably is a hole made to gain access sometime to the nut, subsequently filled with something; there is a kit sold for the Bravo transome shields that is designed to do that same job ( that kit comes with a plate that is bolted on afterwards).

 

[Searush]

It probably is a hole made to gain access sometime to the nut, subsequently filled with something; there is a kit sold for the Bravo transome shields that is designed to do that same job ( that kit comes with a plate that is bolted on afterwards).

Now that (plus a bit of sealant) seems a far more seamanlike solution. Your friend may need access to that nut again sometime.