1983 Mercury 50 hp tilt motor issue

[DeepCMark58A]

So last week I picked up a fishing boat it has a 1983 Mercury 50 hp with tilt. Motor runs great but the tilt only operates when hitting the down button not the up. One solenoid had been replaced before I bought it so I did the easy $12.00 fix and bought the other solenoid installed it and same result. I did an inspection of the wires and nothing is frayed appears to be in good shape.

Since many issues and failures have the same common cause where should I check next? I know I need to have a manual unfortunately it will not be delivered till next week, using a volt meter is problematic as well because I am home alone this week.

 

[Texasmark]

Most units (of which I am familiar) bring 12v from the battery to the center wire of the Up-Down switch. then one of the Single Pole Double Throw (SPDT) other terminals (3) delivers that voltage to one of 2 solenoids (relays) which are wired to apply the voltage to the tilt motor in opposite directions.....like up is +/- and down is -/+ to the motor terminals.

I'd go to the switch, verify 12v to the switch and then measuring at each outer terminal, move the switch to the UP-DOWN positions and see that the voltage follows. If not....new switch....ebay has SPDT switches for a song......generic device. If so, check wire to UP solenoid for 12v at the solenoid when UP is pressed. If that's gook, go to the OHMS scale on your meter and check the ground terminal for the solenoid to have contact back to battery - usually through a contact on the engine block proper. Then check to see that the power/ground wires to the motor from the UP relay are intact. Since you have a new solenoid, somewhere along the line you should have discovered the smoking gun.

You didn't say what solenoid you used as your replacement. If the same OEM part number then disregard the following. If not: The solenoid is an electric switch using a low current control circuitry to operate a high current switch (really....daaaaaaa).

It has the high current set of contacts but needs the low current control circuitry to operate. The low current circuit has to have both sides of the battery across it. Some relays are like the ones used (used to be used) in your automobile and had 2 ⅜" stud, high current terminals and either 1 or 2 low current (control) terminals for activation. The ones with only 1 terminal, are internally wired to the bracket and through the bracket they get the - return to the battery.....with a bi-directional motor requirement where both polarities change to change direction you won't be using the single control type solenoid/relay.

Other relays are in a rectangular, plastic encased housing with pins that plug into a socket, and others have exposed terminals that are soldered to the connected wiring. Commonality of parts says that both would be the same part number/type......just a little bit of info if you need it fine, if not so be it.

Well it's 4:20 and I'm getting sleepy so I think I'll go back to bed and maybe back to sleep.

 

[jimmbo]

There are a few pages here with wiring diagrams, further towards the front, there is the Service Section for power trim
http://boatinfo.no/lib/mercury/manuals/mercury_1965-1989_40-115.html#/532

 

[DeepCMark58A]

Thank you for the info, I located my meter leads with clips so I can extend the reach and run a volt meter and hit the switch.

 

[Chris1956]

A lot of those Mercs have trim limit switches. Try pushing the trailer button (newer controls) or middle and top buttons together (older control panel), and see if that works. If she trims, the trim limit switch is likely bad.

 

[DeepCMark58A]

Nope the trailer button delivers the same result.

 

[Chris1956]

Jumper voltage from Battery positive post to blue wire (to PTT motor) on up solenoid secondary winding. If motor does not spin, motor is likely bad. If motor does spin, it is likely trim switch is bad and trailer button is wired incorrectly.

The trim limit switch is located in the starboard trim cylinder bracket. They commonly break. Trace the wires from the trim limit switch to the main PTT harness. You should be able to unplug the trim limit switch and put a jumper (2 bullet connectors) between the connects to bypass the trim limit switch.

 

[DeepCMark58A]

I got out to the shop briefly, checked voltage at the solenoids. Hooked up and checked both solenoids. Connected to where each wire that goes to the tilt motor. Had 12 volts on both solenoids when the switch was activated both up and down.

 

[jimmbo]

And no volts when the switch was not touched?

 

[DeepCMark58A]

Correct.

 

[jimmbo]

If power is going to both Solenoids, regardless which is being selected, then there are some crossed/shorted/miswired wires in the system

 

[DeepCMark58A]

No I checked them individually and also cross checked, one solenoid gets voltage when I hit up, and the other gets voltage when I hit down. Power is being supplied thru the solenoids as it should be.

 

[Chris1956]

Well, you have a bad ground on the trim motor, or the trim motor is bad. Some of those trim motors had a bi-metal circuit breaker on them (under the casing). They could get some dirt between the contacts, causing an open circuit.

 

[DeepCMark58A]

Do they have two grounds going to the tilt motor, and two circuit breakers? One for up one for down? I am sorry to be asking pointless questions I am stuck in the recliner again today, I will get out to the shop later to verify the ground issue.

 

[Chris1956]

That motor has a single ground. I am not certain it has any circuit breakers, I know my '77 didn't.

You should look up "types of DC motors" and find a center ground winding type motor. That is the kind used in your PTT.

Voltage is fed to one of the ends of the winding to produce motor spin in the UP direction. Voltage is fed to the other end of the winding to produce motor spin in the down direction. You might ohm out each of the windings to make sure neither are open.

 

[DeepCMark58A]

I was wondering if you can meg a DC motor, glad to know that unlike the AC motor we need the contacts to be closed.Will make it simple to test.

 

[DeepCMark58A]

Both contacts test closed. I will have print the schematic at work tomorrow and get back at it.

 

[Texasmark]

I was wondering if you can meg a DC motor, glad to know that unlike the AC motor we need the contacts to be closed.Will make it simple to test.

I used to use a megohmmer for troubleshooting high voltage transmitters....like 30kv and up.....LVDC I use a multimeter.