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I purchased a 2003 T8 with a problematic tilt and trim unit. I have worked out the electrical issues, but the hydraulics are not working correctly either. When activated, the electric tilt motor turns at good speed and will move the lift rod when there is no load on the lift rod. However, the movement is slow and cumbersome. Once extended, I can then press the lift rod back in the cylinder with my the force from my hand, so there is some leakage internally. When I press down hard, the reservoir area becomes pressurize - when I remove the fill cap, fluid explodes out. When installed on the motor, the tilt unit tried to move the engine, but does not have enough hydraulic power to do so - again, the electric motor is running fine.
I have talked to two dealers about the situation, and their solution is to replace the entire hydraulic unit (very expensive).There has to be a much more economical answer in this "disposable" age.
I have the unit apart and am trying to understand how it works. Does anyone know of a good manual that explains hydraulic operation?
The electric motor turns two metal gears that make up the pump inside the hydraulic housing. "Tilt up" provides +12V to the motor spinning it one way, "tilt down" -12V spinning the motor the opposite direction. The pump then feeds two channels (one either direction) with one-way check valves at the end of the canal. Each check valve appears to enter chambers in the piston/rod area to move the rod. I assume pressurizing one chamber will raise piston, and the other somehow allows the piston to lower. There are two "Piston Shuttles" at the end of each pump canal opposite the one-way check valves (parts 26 and 27) in the diagram:
2003 T8PXHB Yamaha Outboard POWER TILT ASSY Diagram and Parts
Does anyone know what these do?
Each chamber also is connected to a "pin, absorber valve" (part 42). Again, any input regarding the role of this valve?
Each chamber is also connected to to a pin and ball valve (parts 48 and 49). Any perspective as to the role of this valve would be appreciated.
Finally, there are two relief valves located one the outside of the gear housing assembly (part 37). I assume there are activated if too high a pressure is achieved in the housing as it vent back to the reservoir area.
Any insight or experience anyone has with these pumps would be appreciated. Otherwise, I will start will replacing seals and go from there. But getting an understanding of what the different valves do may help given the symptoms.
Thanks in advance - I know this is a stretch, but it really bug me throwing away an entire unit for what may amount to a problem with a seal or o-ring.
I have talked to two dealers about the situation, and their solution is to replace the entire hydraulic unit (very expensive).There has to be a much more economical answer in this "disposable" age.
I have the unit apart and am trying to understand how it works. Does anyone know of a good manual that explains hydraulic operation?
The electric motor turns two metal gears that make up the pump inside the hydraulic housing. "Tilt up" provides +12V to the motor spinning it one way, "tilt down" -12V spinning the motor the opposite direction. The pump then feeds two channels (one either direction) with one-way check valves at the end of the canal. Each check valve appears to enter chambers in the piston/rod area to move the rod. I assume pressurizing one chamber will raise piston, and the other somehow allows the piston to lower. There are two "Piston Shuttles" at the end of each pump canal opposite the one-way check valves (parts 26 and 27) in the diagram:
2003 T8PXHB Yamaha Outboard POWER TILT ASSY Diagram and Parts
Does anyone know what these do?
Each chamber also is connected to a "pin, absorber valve" (part 42). Again, any input regarding the role of this valve?
Each chamber is also connected to to a pin and ball valve (parts 48 and 49). Any perspective as to the role of this valve would be appreciated.
Finally, there are two relief valves located one the outside of the gear housing assembly (part 37). I assume there are activated if too high a pressure is achieved in the housing as it vent back to the reservoir area.
Any insight or experience anyone has with these pumps would be appreciated. Otherwise, I will start will replacing seals and go from there. But getting an understanding of what the different valves do may help given the symptoms.
Thanks in advance - I know this is a stretch, but it really bug me throwing away an entire unit for what may amount to a problem with a seal or o-ring.
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