2 wire trim motor on 87 115 lower unit

[pancakes]

i've put a 2002 115 powerhead on a 1987 lower unit. i'd like to convert the trim motor from 3 wire to 2 wire. does anybody know if the 2 wire motor is compatible with the three wire pump and trim unit?(both single ram units) i tried the three wire motor by hooking blue and green wires into the relays and grounding the third wire but everything's getting very hot. i know i can also bypass the relays and use a solenoid but would rather keep the relays in tact and use them since it's a better system. thanks.

 

[Chris1956]

Re: 2 wire trim motor on 87 115 lower unit

The pump should be compatable. You might check application data on a replacement motor for your pump unit, to be sure.

2 wire motors require you change out the two solenoids and replace them with relays. Relays change the polarity of the power to the motor. Putting +12V on the green wire and grounding the blue wire causes the motor to run in the down direction. Putting +12V on the blue wire and grounding the green wire causes the motor to run in the up direction. There is no third ground wire.

If the new powerhead has the relay box, you should be easily able to hook up the motor to the relays.

 

[RRitt]

Re: 2 wire trim motor on 87 115 lower unit

if there is not an exact fit 2wire motor then simply convert your relays to support 3w. It is a very easy modfication that can be done one of two ways.

Easiest way -
get two 20A diodes. Hook one to blue wire and one to green wire. Pointy end of schematic symbol points towards the motor. Base of triangle symbol points towards relays. That's it. Done. When the relay flips polarity the diode blocks negative from reaching the blue or green wire. Attach the black wire to engine ground.

Best way -
The Diode takes 0.7v to operate. when your battery is low that can make a difference. So instead of electronically blocking negative just disconnect the black wire from relay post # 87a. But leave the smaller black wire connected to coil control post # 86.