Homer22-
The 1988 Cruisers and Anglers had the pump between the gas tanks in the depression back next to the transom with the water exit fitting on the starboard side (at least all the ones I've seen).
Later models sometimes had the pump located either in a boxed in well just inside the dooorway in the cabin, or in a similar well over to the starboard side midway between the doorway and the starboard side of the hull. This well was accessible under the galley through the right hand cabinet door.
If you have an amidships water exit, it's likely someone has converted your 1988 Cruiser to a later type set-up.
This amidships pump design was intended to alleviate the problem of water standing up next to the cabin bulkhead when the boat was at rest or moving slowly. The problem arose either when rainwater came into a non-moving boat, or when splash water that came in when the boat was moving, but hadn't been fully bailed out before the boat was slowed down. (Moored boats had serious problems from rain!)
This new design solves the problem above, but doesn't really pump out water coming aboard when the boat is underway (on a plane and tilted abaft) as well as the original design.
As a solution, some folks have installed both!
If I had to choose one or the other, I favor the rear solution, as long as I'm using the boat in such a manner that I'm always aboard to monitor the situation and speed up the boat to allow the rear pump to empty the boat. If the boat is going to be moored or docked without a cover over or a covered cockpit, then I think I'd add the amidships pump as well.
This topic and it's discussion has occupied a lot of space here over the years.
Newer boats have raised deck inserts or a raised flat deck that alleviate the problem. They both keep your feet dry, and either hide the water underneath themselves in the first case, or in the second force it to the rear bailing well.
Hope this makes sense!
Can you tell where the pump is from the sound? Be sure you've tested it with water covering the impeller well before you replace it, it might just be spinning dry!
Good Luck!
Joe. :teeth :thup