As a former owner of a 1979, 53 classic, the boat came from the factory with 3 water filters 2 of the same model manufactured by---at the time--AMF Cuno, now know as just Aqua-Pure. The filter in the starboard engine room, connected to both the Galley Maid pump and the dockside water is TEEL 1P745 (believe the company has been absorbed by Aqua-Pure) and takes a Aqua-Pure AP117 filter cartridge. (This cartridge is good for Chlorine taste & odor, sediment & rust). The other 2 filters, one under the galley sink which handles the sink cold water and the refrigerator water line and one under the aft wet bar which handles the icemaker and the sink, are Aqua-Pure AP200 and they take a AP217 cartridge. This filter like the big unit in the engine room, reduces sediment, chlorine taste and odor.
The Aqua-Pure line and cartridges are sold at all Furguson Enterprises, Inc plumbing stores. If they do not have the cartridge, they will take an order and mail it directly to you.
My friend has a 1978, 53 classic and his boat has the same filter set up. Unfortunatly, the 54', 1987 MY I now own, only has 1 Aqua-Pure filter, AP510 with a spin on AP517 cartridge filter, under the galley sink for the sink cold water and the refrigerator ice maker. No filter in the engine room or for the wet bar sink.
Hope all this helps in locating replacement filter cartridges.