How to Bleed Hydraulic Tilt Trim Pump for Outboard Motor

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When your outboard motor's tilt and trim control becomes sluggish or "mushy" in its movements, like a newborn, it may need to be "burped" to remove air entrained in the hydraulic oil. The air has to have a place to escape from the system--one function of the hydraulic reservoir--and a bit of hydraulic oil is lost to the pressures of the process. Even so, the change in your tilt/trim control's performance will be noticeable and welcome.

Items you will need

  • Adjustable wrench

  • Plastic catchment buckets

  • Hydraulic oil

Use an adjustable wrench to loosen the hydraulic lines to the pump/hydraulic motor. Set a plastic bucket beneath each loosened line as a catchment for leaking oil. Open the hydraulic fluid reservoir by removing the cap on top of the reservoir.

Operate the trim/tilt control several times. Oil will leak from the loosened lines into the catchment buckets. Re-tighten the loosened hydraulic lines.

Add hydraulic oil to the hydraulic reservoir until the oil reaches the bottom of the filler opening. Leave the reservoir open.

Operate the trim/tilt control several more times. Make sure that no more hydraulic oil has leaked from the lines you loosened, then re-tightened. Check the level of the oil in the reservoir.

Add oil to the hydraulic reservoir if needed. Continue operating the trim/tilt control and adding oil after each tilt operation, until the oil level remains at the bottom of the filler opening. Return the cap to the hydraulic reservoir and tighten hand tight.


  • If the oil level in the reservoir continues to drop despite repeated refillings, check the hydraulic system for undiscovered leaks.
  • Dispose of waste hydraulic oil in accordance with local directives.