Power Tilt and Trim Units
Power tilt and trim units enable the operator to raise or lower the stern drive unit in response to boat speed, load, and varying water conditions.mercury power tilt and trim units These units also permit the drive to be tilted up to allow easier access to the engine for cleaning or refueling. Early stern drives had mechanical tilt systems based on a series of holes in the gimbal ring that could be loosened to allow the drive to be tipped up and down. More recent stern drives have electro-hydraulic tilt and trim systems that consist of a control panel or handle, a hydraulic pump motor, a control switch, trim indicator sender (optional on some models) and a system of hoses and fittings for connecting the electrical sub-system to the ram system.
The most common and convenient type of system is the Mercury Marine "Mercruiser" power tilt/ trim unit, which can be used with MerCruiser Alpha One, R, MR, Gen II and Bravo One and Bravo Two stern drives.mercury power tilt and trim units Other types of hydraulic tilt and trim systems may be fitted to various Mercruiser engines, but are not interchangeable.
A Mercury power trim and tilt system consists of an electric sub-system with a control panel or handle, a pump motor, a trim indicator sender (optional on some engines) and a system of hoses for connecting the electrical sub-system to and from the ram system.mercury power tilt and trim units This sub-system is powered by a 12VDC battery cable from one side of the trim solenoid to the +12VDC terminal of the battery and from the other side to the -12VDC terminal at the trim bracket, through a trim indicator sender relay and an electric clutch.
An additional feature on some units is a switch that allows the operator to select whether the engine can be tilted to allow easier access for maintenance or to clear an obstruction. The switch is also used to disconnect the power tilt and trim system from the engine.
To change the power trim and tilt unit on most older Mercury engines, the steering cables must first be disconnected. This is done by backing off the nut at the top of the tilt tube about 3/4". Then, the bolt at the bottom of the tilt tube must be backed off about 1/4". This gives enough clearance to remove the trim unit.
Be real careful when you disconnect the steering cables. The motor will flop over "fast" and can catch your arm or hand if you are not careful. It's a good idea to have someone else with you while working on the motor, especially when disconnecting the steering cables. It's also a good idea to have a helper when removing the trim unit from the eye of the ram. The nasty little locking pin that holds the cylinder rod end in place is very hard to get out, because it is tucked up under the trim unit and difficult to see.