Volvo Penta AQ125A, AQ125B, AQ145A, AQ145B Inboard Engine Sterndrive Workshop Manual (P/N 7739856-8)

• Covers 1998 Volvo Penta AQ125A, AQ125B, AQ145A, and AQ145B 4-stroke overhead inboard engines, including US-spec and standard sterndrive variants
• Original 74-page OEM publication (P/N 7739856-8, dated November 1998)
• Features detailed exploded-view illustrations, torque specification tables for critical fasteners, and comprehensive wiring diagrams for standard and US-market instrument panels
• Serves as the definitive reference for the AQ125 and AQ145 engine series, detailing assembly, disassembly, and critical clearance tolerances for internal components

Engine Service Coverage

This OEM technical publication details the exact specifications, system descriptions, and rebuild procedures for the standard versions of the Volvo Penta AQ125 and AQ145 engines. While specific illustrations may highlight distinct component variations across the A and B designations, the fundamental overhaul operations remain consistent. Mechanics will find comprehensive tear-down and assembly instructions for the cylinder head, valve train, crankshaft, pistons, lubrication circuits, and fuel delivery systems.

The document also thoroughly outlines the cooling and electrical networks alongside specific carburetor tuning requirements. A dedicated fault-finding chart helps technicians expedite diagnostic evaluations for common marine engine issues like hard starting, overheating, and erratic running. Proceed with caution when servicing marine powertrains; always ensure proper shop ventilation and follow established safety protocols before beginning any fuel or electrical diagnostics.

Technical Data and Specifications

Access critical calibration data required for professional overhauls and bottom-end rebuilds. The text documents precise torque values for vital joints, calling for 90 Nm (in two stages) on the cylinder head and 110 Nm for main bearing bolts. It details specific piston clearances: 0.05–0.07 mm for the AQ145 series and a tighter 0.01–0.03 mm for the AQ125 models.

You will also find the crankshaft end float for the AQ145A specified at 0.037–0.147 mm, along with exact valve spring load data at compressed lengths of 38 mm and 27 mm. Having these factory numbers on hand eliminates guesswork, ensuring your internal components meet strict OEM tolerances during reassembly.