[Saqqara]

Among previous owner maintenance spares I see two sizes of pencil zincs.

The larger one fits the heat exchanger. Where might another thinner one with a smaller head go? It looks like the exhaust elbow may have a zinc in the top, but it is the larger size.

 

[Faster]

Perhaps the PO had a mean streak and simply left it there to drive you bonkers??

I found this old post on another forum by another SNer Stu Jackson.. this might be helpful. Hope you don't mind, Stu....

JoeIf you have the M25 engine, with the 2 inch HX, you'll notice the great design detail of the HX that puts the opening end at the OTHER end of the HX from the zinc. Really helpful. And absolutely useless for your situation.Most of the answers have been right on. The thing is that here are little bits and pieces of the old corroded zinc just laying inside your HX waiting to get clogged inside the tubes and cause you to overheat the engine.When we first got our PO boat in 1998, I was not as comfortable with the engine and its parts as I am now, mechanically inclined or not, and felt much the same as you do.Unless you believe that whenever you conk out there'll be a smiling marine mechanic just waiting to help you out, it's time that you started to learn to work on it, and the HX is gotta be the easist, simplest thing in the world to do.If you have the 3 inch HX, you can take the ends off in place, but you'll still have coolant leaks if the hoses are still connected. Plus you'll have a heck of a time getting back there to see what's inside. You mentioend your MX25 engine, which should be a 3 incher. It may make sense to remove it anyway.If you do, or if you have the 2 inch HX you need to take it off to best service it. All it takes is removing four hoses and the two hose clamps that tie it onto the bracket at the back of the engine.Take it off, check the end cap(s) (if you need a replacement, get one, because the old end caps on the 2 inch HXs tended to be very thin and require replacement, source: SEN DURE 1-800-548-6252)). Jiggle and shake the HX. If it sounds like a mariachi band, there's stuff inside you need to get out. Since the stuff is down on the other end from the cap on the old 2 inch HX, you'll need to keep shaking and poking inside the hose connection until you get it all out. Also check all the other hose connections, since sometimes crud builds up inside the connecting tubes.The first time I did this it took all day. I've only had to do it twice again since we first got the boat, and it's down to about an hour and a half. Good piece of mind to avoid overheating. Use it to change your hoses, too.I'm now scheduled to change my zincs every three months. Lots easier than taking the HX out more often. Last time I had to take it our because I got lazy and waited four months to change the zinc. Dumb of me, because the old one crumbled and left parts inside.Good luckStu

 

[tempest]

Here's the parts manual

http://www.westerbeke.com/OnlineManuals/200142_M25_M25xp_Parts_List.pdf

I see only one listed. But you never know.

The PO left what I thought was a spare impeller onboard with my parts kit. Went to use it once and it was the wrong one.

 

[Minnewaska]

I've always found stuff aboard that didn't belong. PO probably brought it forward from a diff boat. Check manual for you motor(s).

 

[Stu Jackson]

If the zinc fits in the holder that screws into the HX, then you can use it, fat or skinny. There is only one zinc on an M25 series engine, on the HX, nowhere else.

 

[MarkofSeaLife]

Oil cooler.

 

[djodenda]

On my M25 (Not and XP), I also had a zinc mystery. The previous owner had upgraded the heat exchanger. The smaller zinc was left over from the older, smaller, heat exchanger.

I exiled the offending zinc from the boat. It's keeping moss off my roof now.

 

[Saqqara]

I'm guessing it's something like that. I could pitch it overboard and then discover quickly that I needed it. Or I can hang on to it until I sell the boat, passing on the confusion.

Thanks all.