Trojan Boat Forum

Hi Everyone, I have a question about my zincs in the HX's on my GM 350 crusaders (1988ish). I need to know what size zincs to put back, the old were gone when I pulled the plugs, only green corrosions was left. I bought the boat last year, 1978 F32 sedan 321, so I don't know when they were ever changed before. I have some zincs that thread into the plug but do not fit into the hole in the tank. The shaft of the zinc is 1/2" in diameter, the threads are 3/8". The plug itself uses a 11/16" wrench. I 've been cleaning out the holes and they're getting larger but I'm afraid of taking out metal instead of corrosion. Should this 1/2" zinc fit in the heat exchanger? Or do I need to go to a thinner one?

sounds like corrosion is blocking the hole to me


And welcome to the site

Remove the end plate on the exchanger and clean out the old zinc. If needed run a tap in the hole to clean up the threads. (can get a tap loaner from auto store).

I've problems with some of my replacement zincs, and had to grind the edges off the end a little to get them to fit correctly.

Thanks guys!