1999–2004 Mercury M2 Jet Drive 210 HP Carbureted / 240 HP EFI Service Manual (P/N 90-877837)

Mercury Marine service manual 90-877837, November 1999 edition, covers the U.S.-market 1999–2004 M2 Jet Drive 210 HP carbureted and 240 HP EFI power packages. Coverage spans Important Information, Electrical, Fuel System, Powerhead, and Pump Unit, with separate procedures for the two fuel and ignition configurations.

• Powerhead repair: Removal, teardown, cylinder-bore inspection and honing, piston and crankshaft service, reed-block inspection, and reassembly with component-specific torque sequences.

• Ignition and starting: Switch-box and CDM troubleshooting, DVA tests, charging-system checks, starter overhaul, and separate engine wiring diagrams.

• Fuel systems: Carburetor synchronization, Turn-Key Start enrichment tests, EFI pressure and injector checks, vapor-separator service, and Throttle Position Sensor adjustment.

• Oil injection: Pump bleeding and synchronization, drive-gear replacement, oil-delivery testing, and warning-horn troubleshooting.

• Cooling and maintenance: Water-pressure diagnosis, temperature-sensor testing, cooling-flow diagrams, seasonal maintenance, flushing, and storage procedures.

• Jet pump and installation: Pump-stator inspection, impeller-to-wear-ring clearance checks, shaft bearing and seal replacement, pinion shimming, gear-backlash measurement, and cable adjustment.

Written for Mercury dealer mechanics and service personnel, this manual assumes familiarity with marine-engine service and the required hand tools and special equipment.

Carburetor and EFI Service

210 HP carbureted model: The carburetor section explains idle, off-idle, main, and back-draft circuits, with cylinder-specific jet locations and float-setting procedures. Turn-Key Start (TKS) ECM coverage addresses the enrichment valve, cold-start timing control, and temperature-sensor checks.

240 HP EFI model: Separate low- and high-pressure fuel-flow charts lead into pulse fuel pump, regulator, injector-harness, and fuel-delivery tests. The Fuel Rail Electrical/Fuel Determination chart helps distinguish a supply problem from an injector electrical fault before unnecessary manifold disassembly.

Vapor-separator and induction-manifold procedures cover removal, disassembly, seals, filters, fuel rails, and reinstallation. The electric fuel pump is replaced as an assembly; its internal parts are not individually serviceable.

TPS adjustment uses the Digital Diagnostic Terminal or a digital meter with the specified test harness. Some MAP-sensor and deeper ECM checks refer to separate diagnostic-tool manuals.

Ignition Circuits and Electrical Testing

Electrical coverage separates the 210 HP switch-box system from the 240 HP CDM system. CDM stop-diode flowcharts, stator resistance checks, and starter-circuit troubleshooting support fault isolation alongside the model-specific wiring diagrams and sensor resistance graphs.

The EFI pump voltage-test section warns that prying terminal boots with a metal tool can damage the pump or ECM because the terminals remain powered with the engine off.

Powerhead Rebuilding and Cooling

Internal engine work includes crankshaft bearing and sealing-ring inspection, connecting-rod assessment, piston identification by cylinder bank, and piston-ring installation. Port and starboard component views and powerhead torque-sequence drawings support disassembly and reassembly.

The honing section specifically addresses residual abrasive, which can rapidly wear new rings, cylinder walls, and bearings if cleaning is inadequate.

Cooling diagnosis follows water through the cylinder block, adaptor plate, exhaust expansion chamber, and bypass circuit. The Model 210/240 Water Flow Diagram accompanies pressure checks and an overheating diagnosis chart.

Jet Pump Overhaul and Installation

Drive-housing procedures extend to pinion- and impeller-shaft removal, bearing and seal replacement, and shim selection. The manual identifies the Jet Pump Tool Kit 91-809957A1 and the dedicated preload and backlash measuring tools.

Installation coverage includes hull-cutout and tunnel-dimension drawings, ride-plate sealing, trim-plate adjustment, steering and shift-cable setup, and bilge-siphon installation.

Pressurized fuel, ignition voltage, and rotating machinery require the precautions described in the manual. This overview identifies the documented work; it is not a repair procedure.

Examples of EFI Pressure, Timing and Impeller Torque

These figures are a small selection of the manual’s fuel-system, ignition, and pump specifications.

For the 240 HP EFI, regulated injector-line pressure is 34–36 PSI (234–248 kPa). The 210 HP maximum ignition-timing specification is 24° BTDC at cranking speed.

The jet-pump installation section specifies an impeller-nut torque of 150 lb. ft. (203 N·m), distinct from the impeller-shaft gear-nut specification.

PDF Navigation, Diagram Detail and Page Count

Search and wiring detail: Searchable text is available throughout the manual. Six embedded bookmarks cover only the opening four pages. Small wire-color codes and connector numbers in the engine wiring diagrams are legible when enlarged.

The download is one printable, English-language 409-page PDF. That total includes the original cover and three introductory pages, followed by 405 section pages.