The missing zinc

[JoeK]

So I was doing my annual zinc replacement in the heat exchanger of the Universal engine in my 2002 Catalina 28. I do it once a year as it only disolves about 50% in a season here in the Barnegat Bay. This year, the entire zinc was missing. Nothing left. See the attached picture. Could it be that the zinc somehow unscrewed itself from the brass nut and is sitting inside the heat exchanger just waiting to clog up my cooling system? Can I just take the end cap off and look inside? Will I need to replace a gasket? Any advice will be appreciated.
Joe K

 

[RitSim]

You should be able to remove the end cap without issue - maybe find more than one zinc. Also lets you check the condition of the tubes. I've reused the rubber gasket. In a pinch, you can use a thin film of Loctite Gasket Eliminator to both sides of the rubber. The Gasket Eliminator is like purple vaseline so a thin film is easy to do.

 

[Davidasailor26]

Should be no problem removing the end cap to inspect. That’s not a bad idea to do periodically anyway in case any debris has gotten caught in there, especially if you don’t have a raw water strainer. The gasket should be reusable, at least is was on our Universal M12.

 

[Ward H]

Could it be that the zinc somehow unscrewed itself from the brass nut and is sitting inside the heat exchanger just waiting to clog up my cooling system?

I buy ones that happen to be a bit long and cut them to length with a Dremel cut off wheel. The zinc sometimes comes loose from the brass nut.
It could I suppose thought I doubt it if it is full length. Appears to me there is not enough clearance for a full length one to unscrew completely.

 

[jssailem]

I learned from @LeslieTroyer that the BoatZincs.com (BoatZincs.com (978-841-9978) - The Online Superstore for Zinc Anodes) is an excellent source of the exact sized zinc you might need.

 

[Mark Maulden]

It’s probably a multiple pass exchanger so pull the zinc out and see if the rogue zinc can be pulled out with a dental pick. Available through your dentist or Harbor Freight..

 

[jssailem]

Joe, depending on how long it has been since the Heat Exchanger has been serviced, it may be time for more than a look.

I knew the previous owners had not serviced my HE. So when I could not remove the zinc fitting, it was time to remove the HE and do the job properly. Once I removed the hoses and the bands holding the HE in place, it came out with ease.

Opening it was straight forward. Here is what I found.


A label showing a company now out of business. A fitting with the zinc gone. Some interior channels that look clear and others that are suspect. I ordered a new cover and gasket kit. Took the HE to a radiator shop. They cleaned it out, removed some stuck stuff in the channels. Pressure tested the HE. Gave the unit a spray of black paint and I reinstalled the hoses, bands, and a new zinc. Started the engine, found one hose clamp needing a tweak and all is again as it should be.

Perhaps your boat needs a tweaking.
Only you can be the judge. This was not a difficult task.