Missing zinc?

[Fireman431]

2001 Mercruiser inboard 7.4L.

Closed cooling system with heat exchanger. No radiator.

I'm looking for a zinc in the cooling system but the manuals don't show or mention one. There are a few brass plugs on the heat exchanger and the thermostat housing, but they aren't zincs (or remnants of). Am I missing them or am I looking for something that isn't there?

Thanks in advance.

 

[Don S]

Re: Missing zinc?

Closed cooling system with heat exchanger. No radiator.

Boats NEVER have radiators, the heat exchanger does the job of an automotive radiator.

Some systems didn't have anodes.
The anode would actually be attached to what looks like a pipe plug but it has threads. Then, what is called a "Pencel Zinc" is threaded onto the plug and screwed into the raw water cooling side of the system, not the antifreeze side.

 

[Fireman431]

Re: Missing zinc?

I understand the pencil zinc. I have replaced them in other boats and in my genset. I looked all over the raw water side of the heat exchanger as well as the complete raw water system. The brass plugs that were pulled dodn't have the internal threads for the pencil zinc and had no remnants of the anode. Any other thoughts?