2001–2010 Mercury 115 EFI 4-Stroke Outboard Motor Service Manual (P/N 90-881980R1)

This Mercury Marine service manual covers the 2001–2010 Mercury 115 EFI 4-stroke outboard, starting at serial number 0T178500. P/N 90-881980R1, November 2001 edition.

• Powerhead repair: Cylinder-head and cylinder-block/crankcase disassembly, internal inspection, bearing selection, valve-clearance adjustment, and timing-belt replacement.

• EFI service: Fuel-pressure diagnosis, injector checks, vapor-separator and high-pressure fuel-pump service, Idle Air Control work, and throttle shutter synchronization.

• Ignition, starting, and charging: Diagnostic charts, sensor voltage and resistance tests, stator checks, regulator testing, and starter-motor overhaul.

• Lower unit and cooling: Gear-housing disassembly, bearing-carrier service, pinion-depth and backlash setup, water-pump rebuilding, and thermostat testing.

• Power trim and mid-section: Hydraulic and electrical troubleshooting, trim-unit disassembly and bleeding, post-repair pressure checks, and adaptor-plate service.

• Maintenance and installation: Service schedules, lubrication points, fuel stabilization, control-cable adjustment, and rigging requirements for single and dual outboards.

Written for Mercury dealer mechanics and company service personnel familiar with outboard servicing and the specified workshop tools.

EFI Diagnostics and Electrical Diagrams

Diagnostic code charts and the fail-safe function table connect sensor faults with changes in engine behavior. Coverage includes the MAP sensor, Throttle Position Sensor, Crank Position Sensors, water-temperature sensor, and oil-pressure switch.

The ignition troubleshooting charts distinguish no-spark, weak-spark, and misfire complaints, helping technicians choose relevant component tests before replacing parts.

Diagnostic-lamp connections differ between the original bullet-connector layout using MIL 99056A1 and the later three-pin lamp-and-harness assembly 91-884793A1.

Ignition timing is ECM-controlled and nonadjustable; the manual documents timing checks, throttle-cam adjustment, and TPS setup after component replacement.

The service chapter covers fuel-rail and vapor-separator disassembly, high-pressure pump replacement, and removal and installation of Idle Air Control and the MAP sensor.

Color engine-wiring diagrams and the Typical Gauges with Tach Signal Converter diagram cover electrical connections. Fuel, water, oil, and power-trim flow diagrams trace the other systems; exploded views identify ignition, fuel-system, and charging components.

Powerhead Inspection and Timing Work

The powerhead chapters cover valve-guide and valve-seat repair, camshaft inspection, valve-pad selection worksheets, and crankshaft and connecting-rod bearing-clearance checks. Cylinder-head fastening is documented as staged tightening with torque-plus-angle requirements.

Camshaft installation includes a specific warning about piston position: incorrect positioning can bend valves while the camshaft caps are fitted.

Lubrication: The manual covers oil-pressure measurement and oil-pump removal and installation. The engine oil pump is non-serviceable; its internal assembly drawing is for reference.

Gear Housing, Power Trim, and Installation

The 2.07:1 gear-housing procedures include propeller-shaft and bearing-carrier reassembly, shim selection, pinion-depth measurement, and forward-gear backlash checks. Gearcase pressure testing checks sealing after reassembly.

The gearcase-installation cautions explain how trapped grease at the drive-shaft end can prevent engagement and damage the powerhead or gear housing.

Power trim: Hydraulic troubleshooting flowcharts, O-ring placement, and pressure verification with test gauge kit 91-52915A6 are included. The trim motor is replaced as an assembly; shock-rod repairs are limited to O-rings and the wiper ring.

Rigging and linkage: Installation material covers clamp/swivel brackets, drive-shaft housing, steering connections, and throttle/shift linkage. Propeller selection charts relate propeller choices to gross boat weight and speed.

Marine engine service involves pressurized fuel and high-voltage ignition circuits; follow the manual's service and safety procedures.

A Preview of Valve, Cooling, and Fuel-Pressure Data

The following valve, cooling, and fuel-pressure figures are a small sample of the manual's specifications. Intake-valve clearance on a cold engine is 0.007–0.009 in. (0.17–0.23 mm).

For thermostat inspection, the specified opening temperature is 122°F (50°C).

Fuel-system data specify 41–44 psi (283–304 kPa) at 1,500 rpm, alongside pressure-regulator and mechanical-pump test procedures.

PDF Navigation and Included Pages

Search and diagram detail: The main text is searchable, with embedded bookmarks for chapters and individual procedures. Some diagram callouts are not searchable. Small labels on the wide wiring sheets require zooming.

One printable 527-page PDF in English. This total includes four opening pages, three notes pages, and three blank or nearly blank pages; no separate supplement is supplied.