Anode Bolts Mercruiser R

[LandLubr]

These are the anodes and bolts from an older R model Mercruiser.

Are these bolts supposed to corrode along with the anode?

From the looks of the bottom set, it seems that once the bolt corrodes in two, the anode is nothing more than a decoration.

These are not the easiest bolts to replace due to their location and being glued or sealed in place. Also, it probably would take someone a long time, if ever, to realize that the bolt had failed.

I'm wondering if it would be a bad idea to replace these aluminum bolts with something... ohhh, I don't know... that doesn't cost $20.00... per bolt!

I believe they also serve a structural purpose as they bolt the bottom of the transom shield to the transom plate.

I would appreciate someone familiar with the R model Mercruiser letting me know if this is normal wear for these bolts and they were meant to be changed every few years or could there be a missing ground strap. Most importantly, is there some way to avoid spending $40.00... for two bolts!!! lol

 

[Don S]

Re: Anode Bolts Mercruiser R

Aluminum is used because of the anodes. They don't corrode away when the transom is dry, only when the transom wood is wet (and probably rotten).

 

[LandLubr]

Re: Anode Bolts Mercruiser R

Thanks for that Don, the old transom does have some rot around the anode bolt holes.


I'm still trying to understand how this system functions. It seems that once the connection is lost through a corroded bolt the anode comes out lookin like a peach, the anode on the intact bolt looks more like the pit.

Anyway, I just got a hunk of aluminum from an auction site and thought I'd show my version of an anode bolt. I don't know if this has ever been done before but the total cost for two bolts..$7.00. I used the square and round from the old bolt, drilled and tapped for a new rod. Darwin award??? I'll stick close to shore till I forget about them.

 

[Don S]

Re: Anode Bolts Mercruiser R

You have to be careful what alloy of aluminum you use. Merc also uses aluminum anodes. If you have the wrong type bolts they could act like anodes themselves and corrode away.

 

[LandLubr]

Re: Anode Bolts Mercruiser R

Copy from the description:

1/2" dia. x 12" aluminum round bar stock (alloy unknown).

Hah, I guess that's what I'll name the boat.

Could you tell me if the rubber washers are meant as a water seal or to isolate the anode in some way. They seem to be more of an isolator only allowing current to come from the bolt threads having the bolt act as a conductor of sorts.

 

[Don S]

Re: Anode Bolts Mercruiser R

Not an isolator, just makes it easier to remove the anode.