Connecting 1978 Mercury Power Trim/Tilt?

[scottrbishop]

Hello everyone,

I can't find another thread that discusses this exactly, so sorry if this has been talked about before.

I am trying to connect a power tilt trim motor to my 1978 Mercury 115. I bought new hydraulic hoses for it and have those all connected. I'm confused about which wires go to which part of the power tilt trim.

I have attached 2 pictures to this thread. One of the pictures shows one black and one red wire that were cut by the previous owner. I'm guessing these are the battery connections?

The 2nd picture is of a mysterious 3 prong plug receptor. Do I need some sort of adapter to wire this to my trim/tilt switch? The switch I have has Blue, Green, and Purple wires.

Any help as to how I can get this wired in would be greatly appreciated. Thanks everyone!

 

[imported_Voyager]

Re: Connecting 1978 Mercury Power Trim/Tilt?

Putting +12V on the Green terminal will activate the solenoid for Down trim, the Blue is Up trim. You can "jump" from the red to the green (or blue) terminal on your solenoid to run the pump.

If the limit switches are in place on your motor, the "up" limit will stop the pump. The purple wire (I think) will bypass the limit switch to let you keep trimming up to the "trailer" position. On a lot of old motors, these switches have failed and usually just get bypassed so the all you have is up and down.

I have the same pump as in your pictures. I just ignored the 3 prong connector and went straight to the appropriate terminal on each solenoid.

 

[scottrbishop]

Re: Connecting 1978 Mercury Power Trim/Tilt?

Thanks for responding Voyager, can't wait to get this things working.

I don't see any blue wire attached anywhere on the pump. Could that be the terminal and nut without a wire in my 2nd picture?

Red connects straight to the battery (black must be the ground I assume..) Do I need to put a fuse in there anywhere?

Hope I'm understanding this right.

Thanks a lot!

 

[Chris1956]

Re: Connecting 1978 Mercury Power Trim/Tilt?

There should be an bimetal overload inside the motor, so no fuse is necessary. At this point, I would make the wiring as simple as it can be.

If you cannot get a wiring harness for the PTT that has the three prong connector, you can rig up your own. The horizontal slot will have +12VDC. The two vertical slots connect to the green and blue wires of the motor. The blue wire connects via the single solenoid (for up). Get a heavy duty toggle switch and mount it on the dashboard of the boat. Run a red wire from the horizontal slot to the common pole of the switch. Run a blue wire from the blue side vertical slot to the bottom pole of the switch (for up), and a green wire (down) to the top pole of the switch. Tape 'em together and tape 'em to the PTT unit. The PTT unit should have a light duty battery cable from one side of the solenoid to the +12VDC pole of the battery. The -12VDC terminal of the battery should be connected to the trim bracket, where the black wire from the motor connects. You have bypassed the trim limit switch, which is superflous anyway. Trim by RPM, Ear and speed.

 

[scottrbishop]

Re: Connecting 1978 Mercury Power Trim/Tilt?

Just in case I can't get the power trim to work by this weekend, is there a way to bypass the power hydraulics and lift and lower the motor just like a manual mounting bracket?

 

[Chris1956]

Re: Connecting 1978 Mercury Power Trim/Tilt?

Scott, There should be a knurled knob on the base of the pump unit. This may be turned CCW to allow manual tilting. The manual tilting is not easy, but it does work.

 

[scottrbishop]

Re: Connecting 1978 Mercury Power Trim/Tilt?

Thanks for the help Chris, I got the motor mounted this weekend and plan on finishing up with the power trim after work today. So the large black wire coming from the engine itself connects to the trim bracket and from the bracket to -12VDC? Hope I'm describing this correctly, can't quite remember without the motor in front of me.

Thanks!
Scott

 

[jimg984]

Re: Connecting 1978 Mercury Power Trim/Tilt?

yes, black is negetive 12 volts

 

[scottrbishop]

Re: Connecting 1978 Mercury Power Trim/Tilt?

Ok, so I've got power running to the trim unit and it's making noise when I jump the solenoids... Good sign I suppose.

How do I go about filling the hydraulic cylinders with oil? I can see a bottom screw and a top screw, as labeled in the attached pictures. Do I want to fill with the motor Vertical or Horizontal? Do I close the bottom screw and fill through the top?

Also, the huge black wire coming from the motor... Is this what connects to the trim bracket? Does it just touch the chassis or do I attach it to -12VDC?

Thanks for any help everyone!

 

[Chris1956]

Re: Connecting 1978 Mercury Power Trim/Tilt?

Scott, The black wire from the trim bracket is the trim limit switch. It should have two individual wires inside the sleeve. The trim pump is wired directly to the battery with two light duty cables.

The top fill screw you identified is actually the bleed screw for the down circuit. The bottom fill screw is part of the casting and machining, and should not be removed. The up circuit bleed screw is on the cylinder, next to where the hoses connect. You fill the pump resvoir and then bleed the cylinders down side first, one cylinder at a time until all the air is out. Now remove the cylinders from the bracket and face the up trim screw up. Now run the pump in the up direction and bleed the cylinder unti no air comes out. Repeat with the second trim cylinder.

 

[scottrbishop]

Re: Connecting 1978 Mercury Power Trim/Tilt?

Another dumb question but... Where is the pump reservoir? On the pump motor I'm guessing, but do I have to take something apart to get at it? Or is it just a fill screw I remove?

 

[scottrbishop]

Re: Connecting 1978 Mercury Power Trim/Tilt?

http://www.cpperformance.com/products/Controls/trim-pumps.htm

Ok, I see what a reservoir is now... a big plastic piece that mounts to the bottom of the trim pump? I'm thinking I must be missing a piece. I'll investigate once again when I get off work.

 

[scottrbishop]

Re: Connecting 1978 Mercury Power Trim/Tilt?

I've attached a picture of my entire trim unit. It the reservoir that large black box sitting under the electronics? Is there an opening I should look for to fill with oil?

Sorry for all the questions. Appreciate everyones help.

 

[Chris1956]

Re: Connecting 1978 Mercury Power Trim/Tilt?

The very bottom where the hoses connect is the control valve. The pump itself is directly above it. The resevoir is above the pump and the motor is the round thing that sticks up highest. The fill is an unpainted slotted screw on the top right side of the resevoir.

 

[scottrbishop]

Re: Connecting 1978 Mercury Power Trim/Tilt?

Thanks so much for the help Chris. I got the motor to trim up and down last night. It was a little jerky and finnicky, but I'm thinking that must be because I didn't have time to bleed the hoses yet.

Were you suggesting that I wire the trim switch wires directly into the 3 prong connection slots and tape it together, or would I wire them onto the solenoids some how? I'll take a look at it once I get home. I can imagine how it would work.

 

[scottrbishop]

Re: Connecting 1978 Mercury Power Trim/Tilt?

Thanks again for the help Chris and Voyager. I bled the trim last night and wired up my up and down switch and it's working beautifully. Now it's time for a nerve-wracking water test. Hope I got my throttle and shift linkages attached correctly.

Thanks!
Scott