1970s–1980s Yanmar 2QM15 & 2QM15G Marine Diesel Engine Service & Repair Manual

This Yanmar service manual covers the 1970s–1980s 2QM15 and 2QM15G marine diesel engines. Both use a vertical, two-cylinder, water-cooled precombustion design, with repair coverage extending from internal engine components to the marine transmission and vessel installation.

Text search, bookmarks, and wiring detail: PDF text search is unavailable. Embedded bookmarks lead to the chapters and main subsections. Small component designations, terminal markings, and wire-color labels in the electrical diagrams require zooming for comfortable reading.

• Engine repair: Cylinder-head and wet-liner service, piston and crankshaft inspection, valve work, timing-gear checks, and engine disassembly and reassembly.

• Fuel and governor: Injection-pump testing, nozzle inspection, fuel-system bleeding, injection timing, and centrifugal governor and injection-limiter service.

• Cooling and lubrication: Rubber-impeller water-pump service, optional tandem bilge pump, thermostat inspection, oil-pump wear checks, and oil-pressure measurement.

• KBW10 transmission: Wet multi-disc clutch overhaul, gear and bearing inspection, shaft-shim selection, and remote-control linkage setup.

• Electrical diagnosis: Starter-motor repair, alternator testing, alarm-circuit troubleshooting, wiring diagrams, and optional tachometer connections.

• Installation and maintenance: Propeller matching, engine mounting, shaft alignment, piping arrangements, operating instructions, and periodic inspection schedules.

Written for engineers engaged in marine-engine service, inspection, and maintenance, the manual assumes existing mechanical knowledge.

Engine Construction and Repair

The engine chapters detail the cylinder block, cylinder head, pistons, connecting rods, crankshaft, and camshaft. Procedures cover wet-type cylinder-liner extraction, liner projection measurement, valve-seat lapping and grinding, valve-guide inspection, valve-clearance adjustment, and crankshaft end-play setting.

The liner section explains how excessive projection, including that caused by rust on the block's liner ledge, can damage the head-gasket packing. Illustrated tooling includes cylinder-liner replacer assembly 124070-92050 and main-bearing replacer 124060-92400.

Fuel Injection and Governor Service

The Bosch-type YPFR-2K injection-pump section covers delivery-valve leakage tests, plunger pressure tests, cylinder-to-cylinder injection timing, and delivery-volume adjustment. Nozzle procedures include spray-pattern diagnosis, seat leakage checks, and shim-based injection-pressure adjustment.

Yanmar cautions against unnecessary injection-pump disassembly; adjustment after reassembly uses a pump tester. The fuel filter, diaphragm feed pump, centrifugal governor, and injection limiter have separate inspection and service coverage. High-pressure fuel testing calls for the specified test equipment and careful handling.

Cooling, Lubrication, and Exhaust

Cooling coverage follows the direct-seawater system, its thermostat bypass, anticorrosion zincs, and Kingston cock. Separate illustrations show the water pump with and without the optional tandem bilge pump.

The lubrication chapter covers the trochoid oil pump, full-flow oil filter, pressure-regulator valve, and primary and secondary oil-pressure measurement. Intake-silencer inspection, exhaust-manifold and mixing-elbow deposits, and breather piping are also covered.

KBW10 Gearbox, Controls, and Installation

The Kanzaki-Carl Hurth KBW10 section details friction and steel plates, shift forks, shaft bearings, seals, and adjusting shims. Forward reduction is 2.14:1 for the 2QM15 and 2.83:1 for the 2QM15G, helping distinguish the gearbox configurations before matching propeller requirements.

Remote-control coverage includes the Morse MT2 one-handle system, decompression control, and engine-stop cables. The manual specifies that a two-handle system cannot replace the one-handle arrangement.

Installation guidance addresses fixed and flexible engine mounts, coupling alignment, stern-tube and propeller-shaft fitting, exhaust piping, and front power take-off arrangements.

Starter, Alternator, and Alarm Diagnosis

Electrical coverage identifies the S114-230 starter, standard LR135-31 alternator, and optional LR155-04 alternator. It includes starter no-load testing, alternator output and continuity checks, oil-pressure and cooling-water alarm circuits, and tachometer connections.

Alternator precautions explain why high-voltage insulation testing can destroy the rectifier diodes.

Technical Reference and Troubleshooting

Inspection tables give wear limits for valve guides, pistons, ring grooves, bearings, and gears. Torque tables, fluid capacities, valve-clearance data, and sealant application charts support inspection and reassembly.

Troubleshooting charts connect hard starting and uneven cylinder output with fuel-injection, compression, and valve faults, helping narrow the inspection to the relevant system.

Engine cross-sections and exterior views accompany performance curves, timing gear train drawings, reduction reversing power transmission schematics, and electrical wiring diagrams. Cooling and lubrication system diagrams show the fluid routes.

PDF Format and Included Pages

One printable English PDF contains 221 pages total: 217 chapter pages, including chapter title and contents pages, plus one front cover, one foreword page, one main contents page, and one back cover. All cover and introductory pages are already included in the total.