1990–1998 MerCruiser Bravo One, Bravo Two & Bravo Three Sterndrive Service Manual #11 (P/N 90-17431--4)

This March 1998 edition of Mercury Marine Service Manual No. 11, P/N 90-17431--4, covers the 1990–1998 MerCruiser Bravo One, Bravo Two, and Bravo Three sterndrives listed above. Engine repair requires the separate engine service manual.

• Drive and gear housings: Removal, disassembly, inspection, lower-unit resealing, U-joint rebuilding, gear shimming, cone-clutch service, and propeller-shaft spline checks.
• Transom assemblies: Gimbal bearing replacement, U-joint and exhaust bellows work, shift-cable installation and adjustment, and gear lube monitor servicing.
• Power trim: Oildyne pump diagnosis, trim-cylinder disassembly, hydraulic leak testing, electrical troubleshooting, and dual power trim operation.
• Auto Trim II: Control-module testing, trim-limit and position-indicator adjustment, mode-switch checks, and system wiring diagrams.
• Power steering: Pressure tests, system bleeding, earlier-style control-valve and booster-cylinder repair, vane-pump overhaul, and multiple-drive tie-bar arrangements.
• Corrosion and shifting: MerCathode system testing, grounding checks, anode replacement, and vacuum-assisted Power Shift troubleshooting and shift-cylinder repair.

Written for dealers' mechanics and manufacturer service personnel, this manual assumes training in servicing these or similar products and familiarity with workshop tools.

Gearcase assembly and serial-dependent parts

Separate drive-shaft housing and Bravo One, Two, and Three gear-housing chapters cover bearing installation, inspection, shimming, and final adjustment. Cone-clutch and shifter revisions distinguish replacement kits by serial range and require compatible parts to remain together, helping identify the correct repair parts before assembly.

Maintenance schedules, troubleshooting charts, torque tables, and torque conversion charts support routine service. Fluid-capacity tables distinguish square and round gear lube monitor configurations.

Gimbal, bellows, and shift-cable work

Bravo transom assembly exploded views identify the hardware involved in minor and major disassembly. The procedures reference bellows sleeve tools and shift cable adjustment tool 91-12427; a Bravo access plug drilling template supports access-hole work.

The gimbal bearing and carrier are a matched assembly; replacing the bearing alone can leave a loose fit. High Performance transom assemblies omit the electrical trim-limit switch and trim-position sender, with separate guidance for a mechanical trim-position indicator.

Oildyne hydraulics and trim controls

Oildyne pressure and leak tests help distinguish pump faults from trim-cylinder leakage before component replacement. The power trim hydraulic schematic and trim pump test gauge kit 91-52915A6 support this diagnosis. The hydraulic pump itself requires assembly replacement; separate procedures service the adapter and motor.

The relief-valve instructions distinguish original valves from preset replacements: loosening an original valve's jam nut changes its adjustment, while replacement-valve jam nuts must remain undisturbed.

Dual power trim includes relay and diode checks. Auto Trim II wiring diagrams accompany control-module diagnosis and the adjustments associated with automatic trim operation.

Steering repairs and MerCathode diagnosis

Earlier steering control valves have service procedures and balance adjustments; later valves require complete assembly replacement. MerCathode controller wiring diagrams, monitor checks, and reference-electrode tests support corrosion diagnosis. The Power Shift accessory chapter adds vacuum-system fault isolation and cable adjustment.

Before beginning drivetrain work, review the manual's safety precautions to prevent personal injury or equipment damage.

Selected trim-pressure and Bravo Three backlash specifications

This is a small selection of the manual's test and assembly data. Oildyne trim-pump pressure specifications are 2,200–2,600 psi for the OUT/UP circuit and 400–600 psi for the IN/DOWN circuit. These figures apply to the manual's dedicated pump-pressure tests.

For Bravo Three gearcase assembly, actual gear backlash is 0.012–0.016 in. (0.3–0.4 mm) after accounting for propeller-shaft spline lash separately from the total reading.

PDF text search, diagrams, and page count

Text search and diagram navigation: Body text supports searching, while some diagram labels are embedded in graphics. There are no embedded PDF bookmarks. The opening section links reference separate chapter files that are not included. Small labels in dense wiring diagrams are best read with zoom.

One printable PDF contains 596 pages, including 14 cover and preliminary pages and 18 further intentionally blank pages within the chapters. The remaining 564 pages contain the manual's service sections. All of these pages are included in the total.