When I bought my boat three years ago, I had them install new engine zincs in the block of the Yanmar. Now I'm trying to remove them and replace them with new zincs. I have the Yanmar manual but there's no mention on how to remove the nuts from the engine. They seem to be really oxidized in. Should I heat the bolt heads and then try to remove them with a socket wrench? Or, how about dripping some penetrating oil on them, letting them rest, and then going back with the socket?

Any advice would be much appreciated.

Thanks

Bob Rude
532
"Mmmmm"

On the rear zinc try removing the plate with the 4 bolts to which the zinc is attached. With this out you can either try removing the fitting with the zinc in it or leave it attached to the plate and just unscrew the zinc. You will have to install a new gasket with the plate reinstallation. The side zinc can be loosened with an impact gun or try an impact tool which you strike with a hammer. After it breaks free try a 1/2" drive socket wrench with a pipe for additional leverage. Reinstall zincs with teflon tape to act as seal and anti-seize agent. Good Luck

I just did this, the zinc on the side of the engine was easy, I have changed it the last two years. Last year I was unable to get the back one off. So I tried harder this year. I ground the hex down to 7/8ths and still could not get it off, so I took off the 4 screws and took the whole thing to a machine shop and they got it apart. If you need the Yanmar part numbers or any more info email me at j30381@aol.com. Also the West marine store near me stocks Yanmar pencil zincs and you can make the rubber gasket out of a regular hardware gasket. What you need from Yanmar is the gasket that goes around the whole assembly.

Regarding the use of Teflon tape when installing the new zincs, I think it is better to have direct metal to metal contact. The Teflon tape insulates the zinc fitting from the engine head, eliminating the protection afforded by the zincs.

It's probably better to use a non-insulating thread lubricant.

The use of the teflon tape was a direct recommendation of the Mack Boring rep at the J Boat get together in RI in March. I doubt that one layer of tape would completely insulate the zinc since the meer act of tightening the plug in place would cut through the tape sufficiently to provide electrical conductity. This can be tested with a VOM.