I recently purchased an oday 30, 1982 model.I am finding that the boat was maintained very poorly. I only recently put the boat in the water, had problems with the diesel. The previous owners never changed the fuel filters. Anyway I was reading the owners manual and it mentioned checking the zinc in the heat exchanger. I was looking today and can't see anything that resembles a zinc, at least nothing that I recongnize. I'm worried about this after finding out about the fuel filters.Can anyone tell me where the zinc's are located.How to go about changing it or them. I didn't notice one on the propeller shaft when I launched the boat. Any help would be greatly appreciated. I would also be interested in anything any of you have done. Like adding more in other locations.I have a Universal 5416 engine (M20).Rich