It's likely a Whale Gusher 10. Very common on Pearsons from that era. The problem was they were aluminum. If you didn't keep up with maintenance, they eventually froze solid. Even when new, it was very hard to pump one of those cockpit mounted pumps for more than 15 minutes at any real volume since they had a very short handle throw and you were sitting down. The only manual pump that really moved water was the Edson where you could stand up and put your body weight into it. Frankly, I think you would be better off with two electric bilge pumps and it will likely cost less. A small 500GPH deep in the bilge for nuisance water and then a 2000GPH mounted 3" higher for emergencies. It will move much more water. Boat's just don't lose electrical power like they did in the '80s because so much on a modern boat requires electricity - chartplotters, inverters, etc. As a result batteries, engines, and alternators are more reliable. By the time the water is high enough to kill the engine the boat is likely lost anyways.