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

• Covers 1990–1998 MerCruiser Bravo sterndrive units, including Bravo One, Two, and Three variants
• Official Mercury Marine publication P/N 90-17431-4, March 1998 edition
• Contains 596 pages outlining component breakdown, removal, installation, and adjustment parameters
• Features 124 exploded-view diagrams paired with specialized torque tables for transom and gear housing hardware
• Serves as the primary reference for Bravo series sterndrive service, component replacement, and system maintenance
• Explains gimbal bearing replacement, MerCathode system testing, U-joint bellows installation, shift cable calibration, and cone clutch servicing
• Details the Auto Trim II system, dual power trim operation, exhaust bellows maintenance, gear lube monitors, power steering valves, and propeller shaft splines

Component and System Documentation

Navigating a major sterndrive overhaul requires precise, organized information. This 1998 Mercury Marine PDF publication segments technical data into logical component groups to keep your workspace efficient. It kicks off with essential general information, maintenance schedules, and troubleshooting charts before diving deep into the hardware. Section 3 specifically breaks down drive shaft and gear housing data for the Bravo One, Two, and Three models. You will find thorough outlines for disassembly, inspection, and the critical shimming procedures needed to maintain proper gear mesh. By providing detailed, step-by-step instructions for tasks like complete lower unit reseals, proper shift cable adjustment, and complete U-joint rebuilds, this manual allows DIYers to confidently bypass an expensive trip to the marine mechanic. Later chapters tackle transom assembly maintenance, power trim systems—including specifics on Oildyne trim pumps—and advanced steering system calibration. Before beginning any drivetrain work, always review the designated safety protocols to prevent personal injury or equipment damage.

Technical Data and Service Highlights

Shop-level service demands exact specifications, and this manual delivers the baseline data required for both heavy line repairs and periodic maintenance. The concrete advantage for your daily shop routine is having immediate access to factory tolerances, which accelerates turnaround times and prevents the costly rework associated with improper gear meshing. It details torque values for all primary fasteners, noting the critical 20–25 lb. ft. (27–34 N·m) requirement for transom assembly hardware. Fluid capacity tables provide specific volume measurements geared toward different gear lube monitor configurations. Mechanics relying on precise tolerances will appreciate the documented reference values, such as the 3–5 lb. in. (0.3–0.8 N·m) bearing preload required for accurate gear housing assembly. Furthermore, the electrical sections supply power trim wiring diagrams across multiple configurations, enabling faster diagnostic work.

To further support comprehensive troubleshooting and reassembly, the guide is packed with specific visual aids, including power trim hydraulic schematics, Auto Trim II system wiring diagrams, Bravo transom assembly exploded views, torque conversion charts, and a Bravo access plug drilling template. When servicing these specific Bravo models, technicians often encounter hidden repair traps. For instance, the manual warns that the gimbal bearing and its carrier are a matched set; replacing one without the other can result in a loose bearing fit and subsequent driveline vibration. Additionally, attempting to remove the factory-installed UP or DOWN pressure relief valves on Oildyne trim pumps by turning the hex jam nut will completely destroy the preset calibration.