inconsistent power trim

[vicrydr]

1986 mercury 175 Power trim sometimes trims up but not down. Sometimes trims down but not up. sometimes works both ways just fine.
Was coming in off the lake Saturday and had it trimmed down. It wouldn't trim up to put it on trailer. I turned around and put the boat on plane and it trimmed up just fine. Put it on the trailer and it won't trim down. What gives? Loose connection somewhere?

 

[Bondo]

1986 mercury 175 Power trim sometimes trims up but not down. Sometimes trims down but not up. sometimes works both ways just fine.
Was coming in off the lake Saturday and had it trimmed down. It wouldn't trim up to put it on trailer. I turned around and put the boat on plane and it trimmed up just fine. Put it on the trailer and it won't trim down. What gives? Loose connection somewhere?

Ayuh,.... Most likely corroded wirin' terminal ends at the pump,...

Disassemble, clean, reinstall, 'n protect what ya did,.....

 

[vicrydr]

Thanks, Bondo. Not sure where the pump is but I'll start looking.

 

[gm280]

Any time you start having intermittent problems with anything and it has switches, and wires and pumps and such, it is almost always like Bondo stated, connections or a faulty switch. As far as finding where your pump is located, follow the hydraulic hose. You will find it.

 

[vicrydr]

Yep. Got it. The pump is outside the boat on the motor clamp/mount. Two wires running into the top of it through a plate bolted on top. Being hesitant to tear into that I traced the wires back to two relays mounted on the side of the motor. One clicked when I tried to trim down, the other activated when I trimmed up. I switched them. Then I was able to trim down but not up (opposite) I got a new relay at auto zone (Duralast 19861) Works fine now. Thanks to all for the replies.