How to Bleed Mercury Outboard Power Trim Lines

by Will Charpentier
Bleed and refill the power trim lines every 100 hours.

Bleed and refill the power trim lines every 100 hours.

You can use the power trim system on your Mercury outboard to "balance" your motor's direction of thrust to provide both a safe and level ride and the best application of power for performance and efficiency. Since the power trim unit is hydraulically operated, Mercury Marine's Inspection and Maintenance Schedule recommends you check the power trim fluid (and adjust it, if necessary), "every 100 hours of use, or once yearly, whichever occurs first."

Turn on the power trim system. Use the power trim control switch to raise your motor. Engage the tilt support lock.

Remove the fill cap for the power trim reservoir an ensure that the fluid level reaches the bottom of the fill hole. If it does not, add power trim and steering fluid until it does so. Replace the fill cap.

Use the power trim control to raise and lower the motor several times. Check the fluid level again and add fluid if necessary. Repeat if necessary.

Items you will need

  • Mercury Precision Lubricants Power Trim & Steering Fluid

Tip

  • Mercury's power trim is a self-bleeding system. By opening and filling the reservoir, then operating the power trim unit, you force air that's trapped in the hydraulic fluid(called "entrained air") out of the fluid. When the fluid level stays even with the bottom of the fill hole after your operate the power trim, there's no air left to bleed.

About the Author

Will Charpentier is a writer who specializes in boating and maritime subjects. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. He is also a certified marine technician and the author of a popular text on writing local history.

Photo Credits

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