Engine Zinc Replacement

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Spanish Dutchman

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Dec 7, 2009
6
Hunter 30 Great Kills Harbor
I have an old (1981) Yanmar 2GM and it has two engine zincs to replace.
One is on the top back side of the engine and I was able to open the cap and replace it. The second zinc is on the side of the engine and the cap/nut will not budge. I have tried penetration oil, wrenches and socks both metric 22mm, 24 mm and English 15/16 with not luck to loosen. I'm getting ready to try heat, any ideas to get to help would be appreciated…. :confused:
 
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larryw

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Jun 9, 2004
395
Beneteau OC400 Long Beach, CA
Heat is a last resort; try vibration first. Tap the top so the force of the blow travels down the thread. Use a small ball peen hammer. Apply penetrant, let it sit for a while, tap the nut sharply several times, try to loosen. Two or three attempts should do it, if not, try a heat gun, not a torch.
 
Rich Stidger

Rich Stidger

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Feb 10, 2004
4,235
Hunter 40.5 Warwick, RI
Not all penetrating oil is equal. Did you try PB Blaster or Kroil? Either of them work much better than WD40 IMO. Wire-brushing the exposed threads will help the oil penetrate.

The other technique I have used a few times is to use an electric impact wrench. I know these are physically large, but if you can get it in it will usually loosen without rounding the head. Another tool that you can substitute for the impact wrench is a hammering driver. Ryobi makes a 18V driver that will fasten or loosen up to about 100 ft-lbs. It is a much smaller tool than an impact wrench.

Heat would be my absolute last resort. Heat often weakens the fastener and leads to failure.
 
Ed Schenck

Ed Schenck

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Jun 2, 2004
5,802
Hunter 37-cutter, '79 41 23' 30"N 82 33' 20"W--------Huron, OH
Are you sure there is a zinc in there? I remember that my old 2QM20 manual showed a zinc where there was not one. I think it had to do with whether it was fresh-water cooled(it was) or not. Maybe a call or e-mail to Torresen or Mack Boring could save you some time.
 
sailaway78

sailaway78

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May 11, 2005
3,431
Seidelman S37 Slidell, La.
I finally gave up

On that zinc. Just flat couldn't get it out of there. And I tried everything, except heat. I figured out that there are two choices on these. You either change them regularly, using lots of anti seize, or don't change them at all.
 
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navigator97

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May 24, 2004
470
Hunter 33.5 Portsmouth, RI
I have a 1990 Yanmar 2GM20F engine and the service manual said thet there were NO zincs in the engine. For what it's worth.
 
zeehag

zeehag

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Mar 26, 2009
3,198
1976 formosa 41 yankee clipper santa barbara. ca.(not there)
inmy ericson i have a 2qm20h yannie-- the zincs are changed out every yr or two--still in decent looking shape. there are 2 of them. the owners manual also has the gm version. didja call yer yanmar distributor or dealer for info?? might get the owners manual on your engine as well--has a lot of goood information.
 
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Spanish Dutchman

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Dec 7, 2009
6
Hunter 30 Great Kills Harbor
Thanks for all the suggestions, there definetly are 2 zincs. I did call Mack Boring and basically they said if I can not get it removed the block would need to be replaced... Obviously, I will keep trying to remove it with all the suggestions posted.... Update to follow on how I eventually get it out...
 
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