How to Check and Top Up Power Trim and Tilt Fluid

If you press the trim switch and nothing happens at all, check the simple things first. Is the battery charged and the battery switch on? Try the trim switch on the engine cowling (if your outboard has one) as well as the one on the throttle handle. If the cowling switch works but the helm switch doesn't, the trim unit is fine and the fault is in the helm switch or its wiring.

Look for a trim fuse or circuit breaker near the battery, at the helm or on the engine harness, and replace any blown fuse with one of the same rating. Then have a helper press the trim switch while you listen near the engine. A click from the relay (or solenoid) means the switch is sending a signal. No click usually points to the switch, the relay or the wiring between them.

Works one way but not the other? Many trim systems use a pair of relays (one for up, one for down), and on many of them each direction also depends on the other relay's resting contacts. So a trim that goes down but not up can be caused by either relay. If you replace one and nothing changes, test or swap the other one too before blaming the trim motor.

Corroded connectors, relay sockets and quick-disconnect plugs are among the most common causes of trim failure. Turn the battery switch off, unplug the trim motor connector and the relays, and look for green or white crust. Clean with electrical contact cleaner, reconnect firmly and test again.

Yamaha points out that a connection can look clean and still be corroded where the two parts touch. For battery and ground cables, take the connection apart, clean both faces down to bright metal, and retighten. Loose or dirty connections cause the "works sometimes" trim that drives owners crazy.

If the trim motor keeps running after you let go of the switch, turn the battery switch off right away. That is usually a stuck relay or a shorted switch, and it can burn out the trim motor or run the motor hard against its stops.

• Nothing happens and the trim motor makes no sound: an electrical problem (battery, fuse, switch, relay, wiring or the trim motor itself). Keep going with steps 1–3, then see "When to call a pro".
• You hear the trim motor run but the engine doesn't move, moves slowly, or won't stay up: a hydraulic problem. Go to the fluid check next.

Tilt the motor to the position your manual specifies. If that is fully up, engage the tilt support lever or tilt lock and add a block for extra safety before you work around it. Turn off the battery switch so nobody can trim the motor while your hands are near it.

Find the reservoir fill plug (on outboards, usually on the side of the reservoir between the clamp brackets; on many sterndrives, a cap on the reservoir in the engine compartment). Wipe the area clean so dirt or salt can't fall in when you open it.

Remove the plug slowly. On many outboards the reservoir is full when the fluid is at the bottom of the fill hole; on reservoirs with marks, read the level against them. Your manual gives the exact method.

Look at the fluid on a clean rag:

• Clear and clean: good.
• Milky or cloudy: water has gotten in. Water can cause problems even if the trim still works. Have the unit drained, refilled and checked for the leak.
• Dark, with metal flakes or a burnt smell: the pump is likely worn. Get it checked.

Add the specified fluid a little at a time with a funnel or squeeze bottle until it reaches the correct level. Don't overfill; extra fluid will push out when the rams retract. Check the O-ring on the fill plug and replace it if it is cracked or flat, then reinstall the plug snugly. Do not overtighten.

Remove the support, turn the battery switch back on and run the motor fully up and fully down several times. This pushes trapped air back into the reservoir. Return to the checking position and recheck the level, topping up again if needed. If the motor moves in jerks or makes a groaning or popping sound, there may still be air in the system; cycle it a few more times.

If the motor slowly sinks while running or trailering, or kicks up when you back off the throttle or shift into reverse, check the manual release valve first. It must be fully closed for the system to hold.

With the motor down or supported, turn the valve clockwise until it is snug. Don't force it hard; it is a small valve. On most units you open it only a couple of turns counterclockwise to tilt the motor by hand (for example, when the battery is dead), and you should never unscrew it completely. Always close it again before you run the engine. An open valve means the motor can kick up out of the water in reverse, which is dangerous.

With the motor tilted up and supported, look at the trim and tilt rams, hose fittings and the trim unit body for wet fluid, drips or crust. The ram seals are a common leak point. Seals wear out from age and sun, but also from pitting and corrosion on the ram itself. If a ram is pitted, new seals alone will not last.

Lower the motor, start the engine with cooling water supplied (in the water, in a test tank, or on external flush muffs on an outboard; never on the built-in flush port, which is only for flushing with the engine off) and test trim up and down, then on the water. It should move smoothly, hold its position at speed, and not creep down when you stop pressing the switch. If it still creeps down, the internal check valves or seals are likely leaking, which is a shop repair.

Rinse the trim unit with fresh water during your normal flush. Wipe a light coat of marine grease on the exposed tips of the trim rams. For storage, retract the rams fully so the polished ram surfaces sit inside the fluid and stay protected from corrosion. If the motor must stay tilted up (for example on a mooring), Yamaha's method is to hold it up with the built-in tilt lock or an engine support, then press trim down until the rams pull fully back into the unit.