Power trim on older Mercury 175 problems

[Geshka]

This is new (to me) 1977-ish Merc v6 175 outboard with power trim. It was stored for the long time outside and I am trying slowly bring it back to life.
I connected fresh battery and tried to move it up and down with power trim buttons on remote side mounted control unit. I can hear click (possibly relay) in down direction and no any sound in up direction (I assume it is on limit switch) . No sound of hydraulic pump and no movement (of course) of a trim cylinders. Battery is OK - it is fresh and fully charged.
Asking common wisdom on where to start and what to check first. Let me know if picture(s) of power trim unit is required. Any advice would be much appreciated.

 

[Chris1956]

The PTT motor is likely a 3 wire (up, down, ground) version. I would check to make sure black wire has a good ground.

Then jumper +12VDC to blue wire on PTT motor for up and green wire on PTT motor for down. If the PTT motor works, your issue is in the PTT solenoid wiring.

A wiring diagram should be avail at the maxrules web site

 

[Geshka]

Thanks Chris. I will give it a try

 

[Geshka]

OK, so when I am jumping over relays - pump is pumping and motor is going up and down. Good sign!!!. I am walking along the circuit ad trying to see were is disconnect... BTW schematic on maxrules is quite inaccurate for that series of motors, sorry to say that.

 

[Faztbullet]

There is a trim and limit switch on that unit..reason for the trailer button...

 

[Geshka]

Can you, please, elaborate - what this "trailer" button does?

 

[Chris1956]

The Trailer button bypasses the trim limit switch. When you press it, PTT motor should run in the up direction until motor hits stop, and continue to run.

When your trim limit switch breaks (likely), you may use the trailer button in place of trim up button.

 

[Geshka]

Thanks Chris. Much appreciated. I was hoping this boat is not a major project, but floor is shot, stringers are gone and transom is spongy... Hope motor will not require rebuild.

 

[Faztbullet]

Asking common wisdom on where to start and what to check first.​

Compression test first..

 

[Geshka]

Thanks. What is safest way to make this test ? Should I unscrew all plugs and test cylinders while plugs are out? Any special precautions? Just don't want to make any harm...

 

[Dukedog]

https://maxrules.com/oldmercs/Wiring/1966ona/51.jpg

"in" same as down
"out" same as up