78 omc external powertrim box, do i need it?

[Ronny Jetmore]

i just got a real clean 78 115 evinrude with trim. 3 wires come out of the trim motor and run into the boat. if you directly tap two wires at a time to the (negative and one of 2 positives), you can use the trim.

my question, why do i need the separate little black box that comes with it? the box has a sollenoid and a fuse and a series of wires in it. if i am running my trim directly to the steering wheel, can't i just set-up an inline fuse and eliminate the box altogether?

[Ronny Jetmore]

i meant to say if you tap two wires at a time to the BATTERY. sorry

thanks again

[chris_lacey]

Ronnie, the trim box has relays in it to keep the heavy motor current away from the trim switch. Basically it allows you to control a large current with a small current (at the switch). In short, if you want your trim switch to live, you need the box.

[Ronny Jetmore]

my, control box is an "oldie" and doesn't have a trim switch. i guess i can use the external box and run the wires directly to the swithc on the wheel? is this hard to do?
thanks

[chris_lacey]

Ronnie, I haven't got a manual here at work, but lets see how I do from memory.
From the trim box the cable that goes to the switch has around 5 wires in it. Trim power (red or red/white), trim up (blue or blue/white, trim down (green oir green/white) and the trim gauge wires. You only the the red, blue, green. Hook the red wire to the trim switch common, the blue so it is powered when the switch is activated "up" and the green so it is powered when the switch is activated "down".

[Paul Vaillancourt]

Chris is right in his description of the wiring, here are the diagrams from a 1979 trim unit with the black box.

[Paul Vaillancourt]

heres the handle end of the wiring, the guage uses the brown/black and brown/yellow. From the Box to your trim switch use red/white (for power), Blue/white (down) and green/white (up). If the are backwards just switch the blue and green around.

[Ronny Jetmore]

since my box doesn't have the trim switch at all (it came from a motor that didn't have trim), i can still do this by following the above. anything else to know before i do it?

[Paul Vaillancourt]

It should work fine. The only thing i would worry about is the wire rapping around the steering wheel and that the trim button may not always be in the same position due to the way the steering wheel may be pointing when turning. Espcially if you have hydraulic steering with mine it seems that the steering wheel is always in a different position to point the motor straight so a steering wheel mounted switch would not work for me. I would use the turn signal style switch.