How to Remove the Air From a Trim Pump

by Naomi Bolton

Once the trim pump on a boat is activated through the push of a button, fluid is channelled via valves to the actuators, and the vessel's bow rises out of the water. Air trapped in the hydraulic oil interferes with the outboard motor's tilt and trim function and needs to be removed. The air is bled from the hydraulic reservoir, and the procedure can be accomplished by any boat owner. Once this procedure has been completed, the tilt/trim performance will be immediately improved --- you will once again be able to control how the vessel planes.

Loosen the hydraulic lines to the trim pump with an adjustable wrench.

Place a plastic bucket underneath the loosened lines to catch any oil that leaks.

Remove the cap on top of the hydraulic fluid reservoir.

Operate the trim/tilt control and wait for oil to leak from the lines that your have just loosened. Move the tilt control to the "up" position and then into the "down" position. Ensure that the bucket is positioned correctly to catch this oil.

Pour hydraulic oil slowly into the reservoir. Stop when the oil reaches the bottom of the filler opening. Do not close the reservoir at this point.

Start to operate the trim/tilt control again. Move the control once again upward and then down. Observe the ends of the lines. Continue to move the tilt control first up and then down, until oil ceases to drip form the end of the lines.

Retighten each hydraulic line.

Observe where the level of oil in the reservoir is sitting.

Pour additional hydraulic oil into the reservoir if the level has dropped below the filler opening.

Operate the trim/tilt control again, both to the "up" and "down" positions and observe the level of the oil. Add oil if the level has once again dropped. Operate the controls each time the oil level drops. Cease operating the controls, once the oil level is correct, which is at the bottom of the filler opening.

Replace the cap.

Ensure the cap has been tightened correctly.

Wipe up any oil that may have spilt and wipe down the hydraulic lines.

Items you will need

About the Author

Virtually growing up in a computer repair shop, Naomi Bolton has held a passion for as long as she can remember. After earning a diploma through a four year course in graphic design from Cibap College, Bolton launched her own photography business. Her work has been featured on Blinklist, Gameramble and many others.

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Photo Credits

  • photo_camera Fiberglass Boat image by Wimbledon from