I couldn't find your specific carb number in my Volvo book but the 3.0 liter carbs are usually jetting with 71 or 72 jets and a 2.5 power valve
My 2bbl Holley has a 6 power valve, but it is on a 5.7 and it pull enough vacuum at WOT to close a 4.5 valve
Whenever you replace a carb with a non OEM rebuilt, you run the risk of improper calibration
Have you checked the float height? It sounds like it may be set too high
Carburetor Specifications
3.0GS-A/B Models
Volvo Penta #3857981 500 CFM Model 2300-2V
Pump Lever Clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.010-0.015 in. (0,254-0,381 mm)
Choke Unloader. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.300 in. (7,62 mm) Measured Lower Edge of Plate
Choke Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Notches Lean
Initial Idle Mixture Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Turn Starboard - 1/2 Turn Port Off Seat
Main Jet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Power Valve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5
Float Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Parallel to Fuel Bowl When Bowl Inverted
Choke Vacuum Qualification . . . . . . . . . . . . . . . . . . . . .0.365 in. (9,3 mm) Measured At Lower Edge of Plate
Pump Cam Position (orange cam) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .No. 2 Hole of Cam and Throttle Arm
3.0GS-C Models
Volvo Penta #3863240 500 CFM Model 2300-2V
Pump Lever Clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.010-0.015 in. (0,254-0,381 mm)
Choke Unloader. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.300 in. (7,62 mm) Measured Lower Edge of Plate
Choke Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Notches Lean
Initial Idle Mixture Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Turn Starboard - 1/2 Turn Port Off Seat
Main Jet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Power Valve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5
Float Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Parallel to Fuel Bowl When Bowl Inverted
Choke Vacuum Qualification . . . . . . . . . . . . . . . . . . . . .0.365 in. (9,3 mm) Measured At Lower Edge of Plate
Pump Cam Position (orange cam) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .No. 2 Hole of Cam and Throttle Arm
Fuel Systems
120 VPA 7743454 English 09-2004
3.0GL-B/C Models
Volvo Penta #3863240 500 CFM Model 2300-2V
Pump Lever Clearance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.010-0.015 in. (0,254-0,381 mm)
Choke Unloader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.300 in. (7,62 mm) Measured Lower Edge of Plate
Choke Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Notches Lean
Initial Idle Mixture Setting1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3/4 Turn Off Seat
Main Jet - Port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Main Jet - Starboard. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.1
Power Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5
Float Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parallel to Fuel Bowl When Bowl Inverted
Choke Vacuum Qualification . . . . . . . . . . . . . . . . . . . . 0.365 in. (9,3 mm) Measured At Lower Edge of Plate
Pump Cam Position (blue cam) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . No. 2 Hole of Cam and Throttle Arm