My 85 TR Cat27 has a Universal M-18, which has a smallish heat exchanger that is electrically insulated from any engine metal (tied down into the brackets with nylon ties, and insulated to the brackets by a layer of cut-open hose). I find that I have to replace the pencil electrode every other month at low engine use, and as often as every 10 hours of engine use. Any ideas what might be happening here? Cheers, Hans
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exchanger zinc
I'm anxious to see what others have to say on this topic. I recently bought a 1087 Catalina 27. That the zinc was never even mentioned in the boat maintenence manual. I checked it by accident and found it totally used up. I have seen some people say that it isn't even necessary. Considering your story it seems to be critical.
I'm anxious to see what others have to say on this topic. I recently bought a 1087 Catalina 27. That the zinc was never even mentioned in the boat maintenence manual. I checked it by accident and found it totally used up. I have seen some people say that it isn't even necessary. Considering your story it seems to be critical.
HX Zincs
The zincs are there because there is salt water running through the HX. I assume you have fresh water cooled engines, or else you wouldn't have heat exchangers. This has NOTHING whatsoever to do with electricity. These sacrificial zincs need to be replaced to prevent the HX itself from wasting away from galvanic corrosion from the sea water. Most manuals don't tell you about them. Of course, you need to read up on this. Try the www.catalina30.com or www.c34.org websites and learn about them. Use the search engines for "pencil zincs," "heat exchangers," and any other topics you think'll get you to the subject. You should always have backup zincs on board, and check it regularly. DON'T put pipe thread tape or goop on the threads, you need the brass thread of the zinc holder to touch the thread of the HX directly.
The zincs are there because there is salt water running through the HX. I assume you have fresh water cooled engines, or else you wouldn't have heat exchangers. This has NOTHING whatsoever to do with electricity. These sacrificial zincs need to be replaced to prevent the HX itself from wasting away from galvanic corrosion from the sea water. Most manuals don't tell you about them. Of course, you need to read up on this. Try the www.catalina30.com or www.c34.org websites and learn about them. Use the search engines for "pencil zincs," "heat exchangers," and any other topics you think'll get you to the subject. You should always have backup zincs on board, and check it regularly. DON'T put pipe thread tape or goop on the threads, you need the brass thread of the zinc holder to touch the thread of the HX directly.
Sacrificial Anodes and Electricity
In response to Stu's answer, I need to point out that sacrificial anodes get eaten as a result of electrolysis, i.e. an electric current resulting from the differences between the inherent electric potentials of different conductors. In this case, zinc - the less noble metal - dissolves (as ions), "sacrificing" its own electrons for the benefit of whatever more noble metal it is connected to, like the copper/brass of a heat exchanger. That is why it is important to mention that the heat exchanger is actually electrically insulated from other metal objects (like the engine), which in turn may be in contact (bonding) with sea water, in which case the tiny pencil electrode may be responsible for protecting significant metal structures - all by means of electrolytic current (electricity) flowing between connected metal parts and sea water. As I mentioned, in my case, the heat exchanger appears to be insolated - why then do the pencil electrodes disappear so fast? Cheers, Hans
In response to Stu's answer, I need to point out that sacrificial anodes get eaten as a result of electrolysis, i.e. an electric current resulting from the differences between the inherent electric potentials of different conductors. In this case, zinc - the less noble metal - dissolves (as ions), "sacrificing" its own electrons for the benefit of whatever more noble metal it is connected to, like the copper/brass of a heat exchanger. That is why it is important to mention that the heat exchanger is actually electrically insulated from other metal objects (like the engine), which in turn may be in contact (bonding) with sea water, in which case the tiny pencil electrode may be responsible for protecting significant metal structures - all by means of electrolytic current (electricity) flowing between connected metal parts and sea water. As I mentioned, in my case, the heat exchanger appears to be insolated - why then do the pencil electrodes disappear so fast? Cheers, Hans
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