Power Trim and Tilt: Slow, Stuck or Won't Hold, and What to Check

Power trim is the system that tilts an outboard or a sterndrive leg up and down: a small electric pump, a reservoir of hydraulic oil, one or more rams, a pair of relays or solenoids, and a rocker switch on the throttle or the dash. When it works you never think about it. When it does not, you cannot get the leg up to trailer the boat, or down to drive it, and the day is over. The good news is that trim systems fail in a small number of predictable ways, and most of them are diagnosed with your ears and a multimeter before anything comes apart.

Listen first

Press the switch and listen at the engine. Nothing at all, not even a click, is electrical: a blown fuse or breaker, a dead switch, a broken wire in the harness, or no power to the relays. A click from the relay but no motor is the motor not getting power or a seized pump motor, and a click from the motor end with no movement is a motor with dead brushes or a seized pump. A motor that runs but the leg does not move, or moves slowly, is hydraulic: low oil, air in the system, a worn pump or a leaking ram. A motor that runs and the leg moves one way but not the other is almost always one relay or one solenoid, because up and down use separate ones. Trace the symptom to one of those four and you have halved the job.

Electrical faults

Trim motors draw heavy current, so the wiring goes through a relay or a pair of solenoids near the engine, fed by a thick cable from the battery and switched by the thin wires from the rocker. Corrosion is the usual culprit. Check the fuse or the reset breaker on the pump, then measure voltage at the motor terminals while someone holds the switch: full battery voltage and no motor means the motor; well below battery voltage means resistance in the cables, relay contacts or earth strap; nothing means the relay or the switch. Up and down relays are usually identical, so swapping them is a quick test. The dash gauge that shows trim angle runs off a separate sender on the leg and has nothing to do with whether the system moves; a gauge that reads wrong is a sender fault, and a separate job. A battery that is weak enough to make the motor slow is also weak enough to make the engine slow to start, which is why the battery guide belongs in this diagnosis.

Hydraulic faults

Check the oil level the way the maker says, and they differ. Some want the leg fully up before you look at the reservoir, some fully down, and checking in the wrong position either overfills the reservoir or tells you it is empty when it is not. Use the fluid the maker specifies; most systems take a dedicated power trim and steering fluid and a few accept automatic transmission fluid, and mixing the two or using engine oil thickens the mix and slows the pump. Low oil with no visible leak usually means a leak at the ram seals when the leg is under load; look for a wet film on the ram rods and a slick in the water when you trim after the boat has sat.

A leg that goes up but slowly bleeds back down over an hour, or that will not hold trim at speed and creeps up under throttle, has an internal leak: worn ram seals or a check valve in the pump manifold that is not sealing. On outboards there is also a manual release valve, a slotted screw on the side of the trim unit, that lets you raise or lower the leg by hand if the pump dies. If that valve was opened and not fully closed, the leg will not hold; if it is seized, you cannot get the leg up when you need to, so turn it a quarter and back once a season so it stays free. Air in the system, from running the reservoir low, makes the trim spongy and jerky; cycle the leg fully up and down several times with the reservoir topped up to purge it.

Trim and tilt are not the same

Many outboards have two rams: a large trim ram or pair of rams that work in the first part of the travel against the thrust of the propeller, and a longer, lighter tilt ram that takes the leg the rest of the way up for trailering. A unit that trims normally but stalls at the top of its travel, or that tilts fine but sags under throttle, is telling you which ram or which valve is at fault. Trim tabs on the transom are a different system again with their own actuators, in the trim tab range, and are not involved in leg angle at all.

Parts and repair

Relays, switches, motors and seal kits are cheap and most of the repair is access and patience. Complete trim pumps and assemblies for Mercury, Yamaha, Evinrude, Johnson and Suzuki are in the power trim and tilt range, and for an older engine where a new unit is not made, our used trim and tilt assemblies are tested before they are listed. Volvo sterndrive trim pumps, cylinders and relays are matched by drive serial in the Volvo Penta pumps range. Whatever you replace, clean every earth connection on the way, because half the trim systems that come in dead have nothing wrong but a green terminal. If you want the right relay or seal kit for your engine, ring 0412 532 984.