1972 Mercruiser I/O anodes

[muskrat808]

My 18 ft StarCraft with the 140 Hp Mercruiser I/O has a thin rubber gasket that sits between the hull and anodes . Replacement anodes from West Marine do not have this gasket . My question-what's the purpose of the gasket and if is important,why not included with replacement anodes? I would think you would want more contact with the hull not less ,or is the bolt it screws on to enough of a bonding connection ? Thanks

 

[Ike-110722]

is this an aluminum hull?

 

[fishrdan]

I'm guessing the gasket is to seal water out of the bolt/anode threads, so the threads don't corrode and lose electrical contact.

If you haven't removed the anodes yet, I wouldn't, I have a 72 Mercruiser also. Owner of a local parts house told me to leave them alone when I asked about buying replacements, I didn't ask why. I found out when I removed the transom assembly. The lower 2 bolts are made of a special alloy (really light weight) and they were rotted half way through. Corroded is probably a more appropriate term, but I use the term rotted as the bolts looked just like rotted wood. Both bolts were 1/2 gone, and if I would have tried to remove the anodes I would have snapped them. (Then the engine would have to come out, to replace a $50 pair of bolts.......)

 

[muskrat808]

Yes it is an aluminum hull . The bolts actually look fine .

 

[Ike-110722]

The anode is there to protect the aluminum hull. If you get stray current from bad wiring, or you have some dissimilar metals setting up a cell, the anode will be consumed sooner than the aluminum. This can happen even on small boats that are trailered. If the anode looks ok, leave it be. Don't remove or replace it unless it is seriously eroded away. If that happens you should also be looking for the reason why.