1978 Terry ABF 4.7M, 1977 Merc 850: Power Trim

[adambriner]

Hi everyone, just bought this boat, pretty excited. Fired right up in the seller's driveway. Needs a bunch of TLC, but the biggest thing stopping me from getting on the water is the Power Tilt/Trim.
We could hear the motor engage on the Down circuit but not on the UP. Neither of them actually moved the engine. And it was the same symptom for both switches (one on the throttle and one by the engine).

I assume that means that the electric motor is good, maybe just have a bad relay for the UP circuit and maybe I just need to top it off with oil?

Are there any good resources specific to this system that I can research? Google searches are turning up mostly generic stuff which might just have to do. Hoping someone here might know a little more.

 

[Chris1956]

The round head slotted stainless screw on the power trim pump/reservoir is where you fill it. Use 5W-30 motor oil or Dextron III ATF, whichever in in it now.

The pump/reservoir is self bleeding, but the trim cylinders are not. There is a procedure to bleed them. You might search for it, as I no longer have it.

Down is likely a direct connection to the motor, using HD wire and switch. Up is via solenoid. You might check it for operation. Jumper across the solenoid large terminals to operate the motor in the up direction. That will give piece of mind that it is just a bad solenoid or wiring. Those PTT units have a trim limit switch. if it is broken, like most of them, the trim will not operate in the up direction. The trim limit switch is on the starboard trim bracket. It can be umplugged from the harness and the harness jumpered with bullet connectors, to simulate the trim limit switch closed.

 

[adambriner]

Thanks for the great info Chris! I'll have to get diagnosing soon.
Do you happen to know if there is a proper way to drain the oil from the reservoir? I'm not sure what is in there currently.
Or what the "Reverse Lock Operation" means?

 

[Chris1956]

You could always pull a hydraulic hose off the pump/reservoir unit and run the pump, to drain the oil. However, unless it is contaminated, why do that? Stick a q tip into the fill hole and see what color the oil is. Red, clear is ATF, brown, clear is motor oil. The cylinders also have a fair amount of fluid in them. They would need to be bled, using thebleed screws.

The reverse lock keeps the motor from popping up when in reverse. You can turn it off and tilt the motor by hand. Per the instructions, turn the knurled knob all the way CW to turn the lock off. You should be able to lift the motor up and lock it up with the manual tilt lock. it will be difficult to lift it, BTW.

If the motor is raised via the power Trim, the reverse lock will not allow it to go down. Just FYI....

 

[adambriner]

Good advise again, thank you Chris!

 

[adambriner]

Just to update, it was definitely just the relay/solenoid that was bad.
I was able to connect the motor wires directly to the battery positive in both directions and it moved up and down.
I've got a new relay coming today for $20. Thanks again Chris!