Installing trim gauge on old engine that has no gauge.

[redfishsc]

My engine is apparently on it's second or third boat. I discovered yesterday that it has a trim sending unit but my boat has no gauge for it.

I'd like to install a gauge but am struggling to find proper instructions. I own the original shop manual for the engine (1980 70hp Evinrude) but couldn't really make heads or tales from it either.

The trim sender has wiring (seemingly two wires insulated together) that seem to lead up to the engine block but they disappear in the mass of wiring. I can't tell what they hook up to.

I know the gauge will need Ignition (12v purple wire), ground (black), and Signal.

I have easy access to Ignition and Ground via the tachometer wiring but I don't know how to find the signal wire. Can anyone suggest?

 

[Chris1956]

If you found the sender, trace the wire to the boat harness. The wire may be white/tan. Your gauge would use switched DC power and ground plus the sender wire. You might purchase a trim gauge for your brand of motor, as the sending units may be unique to motor brand.

 

[JimS123]

My memory aint so good any more, but I DO remember doing what you did. Back in the olden days I had a 1976 70 HP 3-cyl Evinrude and after installing it I really felt that it needed a trim gauge. The gauge was OEM OMC and as I recall I drilled a hole in the dash and connected some wires following the instruction manual that came with the gauge.

A quick review of my archived literature showed an OMC part number 174679 for outboards. A quick google showed that most sources show "sold out", but I did find one NOS.

 

[redfishsc]

My boat unfortunately has no wires under the dash. All I have is what's in the control box. I did successfully hook up a tach using the black, purple, and gray wires.

Would the trim sending wire be in the control box? I don't recall seeing any other wires in there unused.

 

[JimS123]

My boat unfortunately has no wires under the dash. All I have is what's in the control box. I did successfully hook up a tach using the black, purple, and gray wires.

Would the trim sending wire be in the control box? I don't recall seeing any other wires in there unused.

The control box must have a switch, thus the wires that go to the trim unit must be there.

I just don't remember how I connected it. Why not just buy the gauge and the instructions should show you what to do. Maybe wires from the gauge need to be spliced into others in the box.

EDIT - I don't know if I can provide the link here so I won't. Google "174679 instruction manual" and it will show you the 4 wires that need to be connected, and what the colors are.

 

[redfishsc]

Ok so here's part of the problem. The wire coming out of the trim sending unit was cut when this motor was removed from whatever boat it was on previously. So all I have is the two black wires coming from the trim sending unit. They don't go up into the engine compartment, just capped and wrapped up around the main wiring pigtail.

I'm trying to figure out how this unit ties into the wiring on the engine block.

I have the service manual for this boat. I see several things on it that I don't understand. See attached photo.

The black wires look like they split off and get attached somewhere marked Ω4, Ω3. What does that mean? Obviously this doesn't mean ohms here but I cannot find anywhere in the manual corresponding to this.

There's also the signal wire coming into the gauge being shown split off to Ω1 which again I don't understand.

And, it shows the two black wires being attached to the same bus bar. Won't that just ground them out? Or is this not a bus bar?

 

[stevepro]

Ok so here's part of the problem. The wire coming out of the trim sending unit was cut when this motor was removed from whatever boat it was on previously. So all I have is the two black wires coming from the trim sending unit. They don't go up into the engine compartment, just capped and wrapped up around the main wiring pigtail.

I'm trying to figure out how this unit ties into the wiring on the engine block.

I have the service manual for this boat. I see several things on it that I don't understand. See attached photo.

The black wires look like they split off and get attached somewhere marked Ω4, Ω3. What does that mean? Obviously this doesn't mean ohms here but I cannot find anywhere in the manual corresponding to this.

There's also the signal wire coming into the gauge being shown split off to Ω1 which again I don't understand.

And, it shows the two black wires being attached to the same bus bar. Won't that just ground them out? Or is this not a bus bar?

redfishsc: Did you get your trim gauge figured out? I have a similar setup and might be able to help.