Comprehensive Guide to Removing the Lower Unit on a 1985 V4 Johnson 90hp Outboard Motor

Introduction

The lower unit of an outboard motor is a critical component that houses the propeller, gears, and other essential parts. Proper maintenance and occasional removal of the lower unit are necessary to ensure optimal performance and longevity of your outboard motor. This detailed guide will provide step-by-step instructions on how to safely and effectively remove the lower unit of a 1985 V4 Johnson 90hp outboard motor.

Step-by-Step Instructions

Materials Required:

• Socket wrench set
• Torque wrench
• Screwdriver
• Flat-head screwdriver
• Pliers
• Grease
• Sealant

Safety Precautions:

• Always disconnect the battery before working on the outboard motor.
• Wear appropriate safety gear, including gloves and safety glasses.
• Use proper lifting techniques to avoid injury.

Procedure:

1. Prepare the Outboard Motor

• Place the outboard motor in neutral and turn off the fuel supply.
• Disconnect the drive shaft linkage.
• Raise the outboard motor to its highest position.

2. Remove the Cowling

• Unscrew the screws holding the top and bottom cowlings.
• Carefully lift off the cowlings.

3. Disconnect the Shift Linkage

• Locate the shift linkage rod connecting the lower unit to the gear case.
• Disconnect the linkage by removing the cotter pin and nut.

4. Unbolt the Lower Unit

• Locate the bolts holding the lower unit to the powerhead. These are typically found on the sides and bottom of the lower unit.
• Using a socket wrench, remove the bolts in a crisscross pattern to avoid warping the sealing surface.

5. Tilt and Remove the Lower Unit

• Slowly tilt the lower unit away from the powerhead using a prying tool or a flat-head screwdriver inserted into the gap between the lower unit and the powerhead.
• Once the lower unit is tilted, carefully lift it off the powerhead and place it on a stable surface.

Inspection and Maintenance

1. Inspect the Gaskets and Seals

• Inspect the gaskets and seals between the lower unit and the powerhead for damage or wear. Replace any damaged or worn seals.

2. Inspect the Gear Oil

• Drain the gear oil from the lower unit. Inspect the oil for water contamination or metal shavings. If water or metal shavings are present, further investigation may be necessary.

3. Lubricate and Grease

• Apply grease to the driveshaft splines and all moving parts in the lower unit.
• Replace the drain plug and fill the lower unit with fresh gear oil to the specified level.

Reassembly

1. Position the Lower Unit

• Position the lower unit on the powerhead, ensuring that the driveshaft splines align with the powerhead splines.

2. Tighten the Lower Unit Bolts

• Insert the bolts and tighten them in a crisscross pattern using a torque wrench. The specified torque for a 1985 V4 Johnson 90hp outboard motor is 30 ft-lbs.

3. Reconnect the Shift Linkage

• Reconnect the shift linkage rod to the gear case and secure it with a new cotter pin and nut.

4. Reinstall the Cowling

• Reinstall the top and bottom cowlings and tighten the screws.

5. Reconnect the Drive Shaft Linkage

• Reconnect the drive shaft linkage to the outboard motor.

6. Test the Outboard Motor

• Reconnect the battery and start the outboard motor.
• Shift through the gears to ensure smooth operation.

Common Mistakes to Avoid

• Overtightening the lower unit bolts: Overtightening can damage the sealing surface and cause leaks.
• Ignoring gasket and seal damage: Damaged gaskets and seals can lead to water leaks and premature component failure.
• Using the wrong gear oil: Using the wrong type or viscosity of gear oil can damage gears and bearings.

Why Removing the Lower Unit Matters

• Regular maintenance: Removing the lower unit allows for inspection and maintenance of critical components, such as gaskets, seals, and gear oil.
• Troubleshooting issues: Removing the lower unit can help diagnose and resolve issues, such as water leaks, gear problems, or propeller damage.
• Improved performance: Proper maintenance of the lower unit ensures optimal performance, fuel efficiency, and reliability of the outboard motor.

Benefits of Removing the Lower Unit

• Extended lifespan: Regular maintenance of the lower unit can extend the lifespan of the outboard motor by preventing costly repairs and premature failure.
• Improved safety: A properly maintained lower unit reduces the risk of leaks, gear malfunctions, and other safety hazards on the water.
• Increased resale value: A well-maintained outboard motor with a properly maintained lower unit will have a higher resale value.

Humorous Stories and Lessons Learned

Story 1: The Loose Bolt

A boat owner attempted to remove the lower unit on his 1985 V4 Johnson 90hp outboard motor. After struggling to tilt the lower unit, he realized that one of the bolts holding the lower unit to the powerhead was loose. The lesson learned: Always check that all bolts are properly tightened before attempting to remove the lower unit.

Story 2: The Waterlogged Gear Oil

A mechanic was called to inspect an outboard motor that was experiencing gear problems. Upon removing the lower unit, he discovered that the gear oil was heavily contaminated with water. The lesson learned: Water contamination in gear oil can seriously damage gears and bearings. Regular maintenance, including lower unit removal, can prevent water from entering the gear case.

Story 3: The Missing Keyway

A boat owner replaced the propeller on his 1985 V4 Johnson 90hp outboard motor but noticed excessive vibration when running the motor. Upon removing the lower unit, the mechanic discovered that the keyway on the driveshaft was missing, causing the propeller to slip. The lesson learned: Always inspect the keyway on the driveshaft before installing a new propeller.

Conclusion

Removing the lower unit on a 1985 V4 Johnson 90hp outboard motor is a relatively straightforward procedure that can be completed in a few hours. By following the step-by-step instructions outlined in this guide, you can safely and effectively remove the lower unit for maintenance or troubleshooting purposes. Remember to always take safety precautions and consult the manufacturer's service manual for specific details and torque specifications. Regular maintenance of the lower unit will ensure optimal performance and extend the lifespan of your outboard motor.

Additional Tips

• Use a torque wrench to ensure that all bolts are tightened to the proper specifications.
• Apply sealant to the bolts and gaskets to prevent leaks.
• If you encounter any difficulties or are unsure about any aspect of the procedure, consult a qualified marine mechanic.

Tables

Table 1: Lower Unit Bolt Torque Specifications

Table 2: Recommended Gear Oil Types

Table 3: Troubleshooting Common Lower Unit Issues