MerCruiser MCM TR / MCM TRS Stern Drive Units Service Manual #5 (P/N 90-12935 1085)

• Covers MerCruiser MCM TR and TRS stern drive units, detailing removal, installation, and precise adjustments for both left and right-hand rotation variants.
• Original OEM factory publication (Mercury Marine form number 90-12935 1085), provided as a comprehensive 326-page PDF.
• Features 47 labeled technical illustrations. You get clear exploded-view diagrams for the transom assembly, power trim pump configuration, and propeller mounting.
• This Number 5 edition serves as the definitive reference for TR and TRS series maintenance. Includes the required 10-hour break-in procedures for new or replacement gears.
• Explores the gear housing, drive shaft housing, Oildyne and Prestolite pumps, and steering systems.
• Highlights layup, recommissioning, U-joint cross bearings, gimbal bearing, and the MerCathode system.

Shop Maintenance & Component Documentation

This 1985 manual breaks down the complete disassembly, inspection, and adjustment of the stern drive unit, transom assembly, and power trim system. Before turning any wrenches or lifting heavy drive components, always review the listed load capacities and factory-specified tie-off points to ensure shop floor safety. The text outlines crucial maintenance intervals for the continuity circuit, shift cable pivot points, and propeller shaft lubrication. It gives technicians the specific product application requirements they need to formulate an accurate diagnostic assessment and execute a permanent fix. Detailed chapters map out the removal and installation of the sterndrive units. Step-by-step instructions guide you through complex procedures that typically require an expensive marine mechanic, such as replacing the gimbal bearing, bleeding the power steering system, and overhauling the U-joints. You will find clear references to necessary specialty tools and correct sealant applications to ensure absolute integrity in harsh marine environments during any major repair.

Specifications and Testing Data

Getting the numbers right matters. This publication lists exact torque specifications for critical fasteners, including the mandatory 80 lbs. ft. (109 N.m) torque required for stern drive unit bell housing studs. Inside, a comprehensive maintenance chart details tasks for pre-start, the first 20 hours, and 100-hour intervals. Because proper gear alignment is essential for smooth operation on the water, the guide provides specific tolerances for transom flatness and parallel alignment down to within 1/8 inch. Reference sections include hydraulic pressure ranges and electrical connectivity requirements for the power trim pump systems. To support accurate troubleshooting, the manual includes wiring diagrams, propeller selection charts, cutaway views, cross-section drawings, and hydrodynamic vector diagrams. This technical data specifically covers drives in the 4922285 and above serial range.

When servicing these specific TR and TRS units, a common pitfall involves the shift cable linkage setup. Technicians must ensure they back off the elastic stop nuts on the shift cable brass barrel exactly one-half turn after bottoming out to allow free pivoting, otherwise stiff shifting or transmission failure will occur. Additionally, neglecting to install the spiral grounding springs on the trim cylinder anchor pins will leave the pivot assemblies ungrounded, leading to severe damage from galvanic corrosion.