1988–1993 Mercury Mariner 100hp, 115hp Outboard Motor Service Manual (P/N 90-13645-2)

This Mercury service manual, publication 90-13645--2, covers the 1988–1993 Mercury Mariner 100hp and 115hp 4-cylinder, 2-cycle outboards. The PDF set includes electrical, fuel, lower-unit, and power-trim service sections; Section 4B, the four-cylinder powerhead chapter, is not included.

Finding tests and reading diagrams: Section text is searchable, and each PDF has embedded bookmarks. Some labels within drawings are not searchable. Small wire-color codes and connector numbers in dense wiring diagrams are readable with magnification.

• Ignition and starting: C.D. breakerless ignition tests, ignition timing adjustments, charging-system diagnostics, and starter overhaul, supported by wiring diagrams and troubleshooting flow charts.

• Fuel and carburetion: Step-by-step carburetor repair and synchronization, fuel-pump service, enrichener testing, and accelerator-pump operation, with separate exploded views for three- and four-cylinder systems.

• Oil injection: Pump bleeding, output checks, linkage adjustment, low-oil sensor testing, and warning-system diagnosis, including distinctions between warning-module and test-button arrangements.

• Lower unit: Water pump impeller replacement, lower unit rebuilds, propeller shaft servicing, gear shimming, and backlash checks, with gear-housing pressure tests.

• Power trim: Design I, Design II, and single-ram systems, including electrical and hydraulic diagnosis, ram service, and motor, relay, or solenoid checks.

• Controls and attachments: Throttle-shift linkage alignment, Ride-Guide steering cable lubrication, swivel pin greasing, and separate installation and service coverage for steering and tiller controls.

Written for Mercury/Mariner dealer mechanics and service personnel trained in outboard servicing and the use of the specified tools.

C.D. Ignition, Starting, and Charging Diagnostics

For electrical diagnostics, mechanics will find precise reference values for the C.D. breakerless ignition system. The Ignition System Test Chart and Starting Circuit Troubleshooting Flow Chart support fault isolation, with stator and trigger resistance tests and ignition-coil checks.

The ignition section identifies Direct Voltage Adaptor 91-89045 for electrical testing. Section 2D contains 12 wiring diagrams, plus the Key/Choke Switch Continuity Test for COMMANDER 2000; its drawings distinguish engine and remote-control configurations. The electrical sections cover 9-, 16-, and 24-amp charging systems.

Working on marine outboard electrical systems involves high voltage and specific hazards. Follow the manual's safety precautions for each test.

WME Carburetors, Fuel Pumps, and Oil Injection

The carburetor tables distinguish WME 11/WME 20 for 100hp and WME 14/WME 21 for 115hp. Four-cylinder synchronization procedures identify the upper pair as the carburetors with adjustable low-speed mixture settings.

The Accelerator Pump Fuel Flow Circuit diagram explains fuel delivery to the third and fourth cylinders. Fuel-pump reassembly warnings explain how incorrect pulse-chamber diaphragm and gasket orientation can block oil delivery and cause extensive engine damage.

Oil-pump output checks distinguish pump versions by part number. The Warning Horn System Wiring Diagram supports diagnosis of the low-oil sensor and warning-module circuits.

Water Pump and Gear-Housing Repair

Gear-housing repair includes pinion-depth setting, forward-gear backlash checks, and pressure testing. The procedures distinguish three- and four-cylinder applications, including four-cylinder backlash tool 91-19660.

Water-pump exploded views separate aluminum- and plastic-base designs, with restrictions on interchangeability. The installation cautions explain how grease at the driveshaft end can prevent correct engagement and lead to powerhead or gear-housing damage.

Power-Trim Faults and Component Versions

Separate electrical and hydraulic troubleshooting paths help locate a power-trim fault before selecting a repair. The single-ram Troubleshooting Flow Diagram is accompanied by leak-down checks for the pump/manifold, pilot valve, and manual release valve.

Date-code breaks identify applicable component revisions and associated faults. The Design I and Design II chapters distinguish serviceable ram and motor components from pump assemblies that are replaced as a unit.

Maintenance References and Powerhead Coverage

Fluid capacities and torque settings for critical assemblies are highlighted throughout the manual to streamline routine maintenance and bench work. Coverage includes cowl removal, storage procedures, compression checks, and tilt-lock lever lubrication, with fresh- and salt-water maintenance distinctions where applicable.

Engine displacement and bore data, spark-plug specifications, and model-specific carburetor settings appear in the reference tables. Section 4A covers three-cylinder powerhead overhaul and thermostat inspection; those procedures are not a four-cylinder powerhead overhaul reference.

PDF Files and Page Breakdown

The manual is divided into section PDFs, with a separate cover and introduction.

This 391-page PDF set comprises 17 files. The total includes the three cover/introduction pages, 16 section title pages, 16 section contents pages, and four blank Notes pages; these are not additional pages.