Power Trim Tilt Assy 8M0090335 8M0171818 for Mercury Boat Engine

Power Trim & Tilt Assembly 8M0090335 / 8M0171818

The Power Trim & Tilt Assembly (part numbers 8M0090335 and 8M0171818) is a key component used on Mercury / Mariner outboard engines, responsible for adjusting the engine’s trim and tilt angle to optimize performance, efficiency, and comfort during navigation.

General Description

• This assembly is also called a Power Trim/Tilt Unit. It allows the outboard motor to be raised or lowered by hydraulic or electric actuation, adjusting the engine angle to match varying load, speed, and water conditions.

• Part numbers 8M0090335 and 8M0171818 are often used interchangeably or as direct replacements for one another.

• The assembly fits outboards ranging from 65 HP – 125 HP, produced approximately between 1988 and 2014 

• It is commonly listed as suitable for Mercury / Mariner 75HP, 90HP (3-cyl) and 100HP, 115HP (4-cyl) outboard engines 

For marine accessory manufacturers or dealers (such as those handling trim tabs and jackplates), this assembly plays an important role:

• It adjusts the propeller thrust angle and engine depth to improve the boat’s running attitude.

• It helps reduce fuel consumption, increase speed, and stabilize performance in varying water conditions.

• When a jackplate or trim tab system is installed, a reliable trim/tilt unit becomes critical to handle the larger movement range and higher loads on the engine mount.

Selection Guidelines

When purchasing or recommending the Power Trim & Tilt Assembly (8M0090335 / 8M0171818), pay attention to:

1. Engine Power and Model Compatibility

   • Always confirm engine HP, cylinder configuration, and year of manufacture.

   • Even within similar HP ratings, mounting dimensions or hydraulic linkage lengths can differ.

2. Part Number Interchangeability

   • Many aftermarket parts list both numbers as interchangeable, but physical verification is advised.

   • Ensure hydraulic fittings, connectors, and wiring layouts are identical before substitution.

3. Electrical System Compatibility

   • Check voltage (usually 12 V), wire count, and control harness compatibility.

   • Make sure the motor bracket and transom mount interface correctly with the assembly.

4. Mounting Space and Fitment

   • Verify bolt spacing and clearance between the trim/tilt unit, jackplate, and transom bracket.

   • Ensure there’s no interference when the motor is fully tilted up or down.

5. Quality and After-Sales Support

   • 1-year warranty 

   • Corrosion resistance and sealing quality are essential for long-term operation in saltwater environments.

Installation & Maintenance Tips

• Disconnect the outboard power supply before installation to prevent accidental activation.

• Check hydraulic oil levels or the electric motor’s condition before use.

• Inspect all bolts, welds, and brackets for cracks—especially if a jackplate or trim tab is installed, as these increase mechanical load.

• Periodically verify that the actuator moves smoothly without binding. Salt, sand, or corrosion can slow operation.

• Use trim adjustment wisely at takeoff, cruising, and shallow water operation to avoid cavitation and improve acceleration.

• Because a failed trim/tilt assembly can directly affect safety and handling, it is recommended to stock a spare unit for emergency replacement.