Yamaha CV25 1990 Service Manual + Outboard Collection (P/N LIT-18616-00-55)

The engine manuals apply to their respective model families. The F45/F50 supplement is used together with the included F50A/F50T base manual.

The Jetdrive book supplements the matching outboard service and owner’s manuals; owner’s manuals are not included.

PDF Search, Bookmarks and Diagram Detail

Navigation and wiring detail: Embedded bookmarks provide chapter and assembly navigation in the manual files. Text search is available in the separate model-to-file index, but not in the manual pages. Small wiring labels require enlargement. Some fine lines and labels in the CV115E wiring diagram are faint or incomplete even when enlarged.

The ZIP contains 23 printable PDFs totaling 3,495 pages: 22 manual files and one reference index. The F50 base manual and supplement share a single PDF. The counts include original covers, front matter and notes pages, plus the reference index and compilation cover sheet listed above.

Powerhead, Gearcase and Ignition Service

The following is a selection of the covered work. Other topics include mounting-dimension drawings and fuel-line routing.

• Predelivery and periodic service: Gear-oil service, anode and battery care, ignition timing, carburetor and throttle-link adjustment, start-in-gear protection, and propeller inspection.

• Fuel-system repair: Fuel tank, meter, priming pump, filter and diaphragm-pump inspection, plus carburetor removal, cleaning, inspection and reassembly.

• Powerhead overhaul: Step-by-step removal, teardown, internal measurement, crank-cylinder assembly, cylinder-head and exhaust-cover installation, and recoil-starter repair.

• Lower unit and brackets: Gearcase disassembly, shim selection, backlash adjustment, water-pump service, leakage testing, and steering, clamp, rubber-mount and tilt-lock work.

• Electrical diagnosis: CV25ED and CV25EMD wiring diagrams, the 703 Remote Control Box schematic, component resistance and continuity checks, and starter-motor overhaul.

• Other engine volumes: Four-stroke valve-train and timing-belt procedures, larger-engine trim-and-tilt systems, and Jetdrive impeller, bearing-housing and liner service.

Yamaha prepared the service manuals primarily for its dealers and trained mechanics, assuming a basic understanding of the mechanical and electrical work involved.

CV25 Controls and Powerhead Inspection

Variant identification: Both CV25 variants list electric and manual starting. The CV25ED uses remote control, while the CV25EMD uses manual control. The identification section illustrates the outboard plate on the port side of the clamp bracket and the separate engine number on the port side of the cylinder body.

Timing and setup: The General Service chapter separates predelivery inspection from scheduled maintenance. Ignition timing is covered using a dial gauge and timing light, with related carburetor-control and throttle-link adjustments.

Internal inspection: Powerhead coverage extends through removal, teardown, measurement, repair decisions and final installation. Inspection addresses cylinder-head flatness, cylinder taper and out-of-round, piston and ring fit, crankshaft alignment, connecting-rod play, reed valves, the thermostat and bearings.

Reassembly identifies bearing and oil-seal direction, piston orientation, ring locating pins, sealing-agent locations, staged fastener tightening and the final free-rotation check. Incorrect powerhead oil-seal orientation is specifically identified as a damage risk.

Fuel-System Inspection and Carburetor Repair

Inspection points cover the fuel-meter pickup and strainer, priming-pump check valves, filter, pump body, valves and diaphragm, and leak-free hose installation.

Carburetor checks address passages, the needle valve, float and pilot circuit. The manual warns that cleaning jets with steel wire can enlarge their openings and seriously affect engine performance.

Gearcase Measurement and Assembly

The lower-unit section distinguishes reassembly with the original gearcase and internal parts from repairs involving replacement bearings, gears or a gearcase. It explains when new shim selection is needed, using bearing-model comparisons, pinion-position measurements, dial-gauge backlash checks and forward/reverse shim-selection graphs.

Clutch-dog and gear inspection, driveshaft and propeller-shaft checks, impeller replacement, water-pump assembly, pressure leakage testing and shift-linkage setup are also covered. These measurements support checking replacement-part fit before final gearcase assembly.

Electrical Testing and Symptom Diagnosis

Electrical repair distinguishes the CV25ED choke-solenoid arrangement from the CV25EMD engine-side starting and stop switches. The CV25 wiring diagrams and 703 Remote Control Box schematic are on PDF pp. 104–105.

Tests cover the pulser, charge, lighting and ignition coils; CDI unit; starter relay; rectifier; fuse; switches; wiring harness; and battery. Starter-motor inspection extends to the pinion, overrunning clutch, brushes, commutator and armature, followed by reassembly and installation.

Symptom charts address no-start, rough idle, stalling, failure to stop and difficult shifting. Their links to component checks help distinguish starting-circuit, ignition, fuel-delivery and mechanical faults before repair work is selected.

Workshop equipment: Yamaha tool references include the YB-1621 test propeller and YB-6139 flywheel magneto holder assembly. Lower-unit work identifies the YB-34232 pinion-gear shimming tool and YB-6265 backlash indicator rod.

Fuel handling, battery service, ignition-timing checks, and work around the flywheel and propeller require the ventilation, fire-prevention, electrical-isolation, test-tank and rotating-parts precautions stated in the manual.

Four-Stroke, Counter-Rotation and Jetdrive Sections

The four-stroke volumes add camshaft, valve and timing-belt work. The 115/130-family and 225/250-family manuals distinguish conventional and counter-rotation lower units, including their separate shimming requirements.

Jetdrive coverage includes assembly drawings, reverse-gate and neutral adjustment, bearing-housing service and liner replacement. Yamaha recommends that Jetdrive overhaul procedures be performed only by an authorized Yamaha Outboard Motor dealer.

A Preview of CV25 Inspection Limits and Gear Backlash

Powerhead inspection: For the CV25ED and CV25EMD, the cylinder-head warpage limit is 0.1 mm (0.004 in.), specified in the power-unit inspection section.

Gear setup: The CV25 lower-unit section gives standard backlash of 0.10–0.25 mm for forward gear and 0.35–0.50 mm for reverse gear. These ranges accompany the bearing-model measurements and shim-selection graphs.