Welcome Don and congratulations on the new to you boat.
No spare parts to help? Bummer. Not unusual.
Know your challenge. Your boat is 20 years younger than mine. I started in a similar place.
My first step was to identify the engine by location of the serial number stamped on the block. It will give you the data on the engine. You can then start identifying the engine parts at a Perkins distributor. With the part numbers I found the consumables that fit by matching the Perkins # to the other part makers like Sierra, Wix, Baldwin etc.
For the impeller you need the pump manufacturer. Should be imprinted on the pump casing or cover plate. Sherwood, Jabsco, and Oberdorfer are typical names used.
A good flashlight, a pen and notebook, and a camera are your friend.
Here is a UK source that can help with Perkins part numbers.
A wide selection of marine version Perkins Perama M30 Engines including overhaul kits, gaskets, oil and fuel filters, seal sets, water pumps, starter motors, alternators
www.parts4engines.com