View Full Version : Yanmar 3gm stuck zinc

02-27-2011, 07:46 PM
I have a 1981 Yanmar 3GM raw water cooled engine with a stuck zinc bolt.
It was the only one left that I could unscrew and replace, and I would do that yearly. However, this past year I have been unable to get the bolt head that holds the pencil zinc loose. I have tried with a cold engine, hot engine, tapping the bolt head, and using a penetrating oil all to no avail. All that has happened is that the bolt head is now a bit worn and will not seat a 6 sided socket without slipping. I am wondering if anyone has any ideas. I am also wondering if hanging a zinc over the side of the boat with an attachment to the engine block will help if I can't get this fixed.

02-27-2011, 09:15 PM
You may have to drill it out. A zink 'overboard' will not help.
Next time use 'never seize' on the threads.