I updated the Subject to "Fresh Water Pump", to try and clarify the terminology. The larger pump is referred to as the "Circulation Pump" and the smaller pump seems to be referred to by many names: seawater, raw water, or impeller pump. Attached is an image of the MD11C from
Volvo Online, where I have highlighted what I believe to be the fresh water "Circulation Pump" on the front of the engine in yellow, and the "Seawater Pump" on the rear of the engine in blue.
Volvo MD11C Fresh Water Cooling System