PVS - Propellor Ventilation System. It's Mercury's adjustable prop ventilation system. It consists holes at the base of each blade of the prop and various plugs. You can use plugs which are either solid or have holes of various sizes to tune your holeshot. The props with the PVS are designated Trophy PLUS (4-blade) and Tempest PLUS (3-blade).
I run a 25 Pitch Trophy Plus on my 200 EFI. During the cooler season, I run it with 2 holes completely closed off and 2 holes wide open. When the weather gets hotter, I'll pull out another plug to help is get on plane quicker. My 25P High Five has fixed holes, but not the plugs for adjusting the holeshot.
BTW -- when it gets REALLY hot this summer, I'll switch to a 24P Trophy Plus to pick up the 300 or so RPM I lose because of the heat.