Help a little old lady with her little old mercruiser 120 wiring?

[MISS demeanor]

Hi. I acquired a 78 Bayliner, Mercruiser 120 with several wiring issues. The first one I'm trying to resolve is the trim. On the red wire to the sending unit (pump) a 20 amp fuse has been spliced in and that keeps blowing. When I disconnect the 2 brown wires going from the coil to the shift interrupt switch it does not. I used to have a 78 Baron (predecessor to Power Play) with a 260 in it 20 years ago, and I did most of the work on it myself, but I'm finding my memory a little foggy as to what's what. Is that spliced fuse necessary?

(by sending unit I mean the hydraulic pump that operates the outdrive)

 

[alldodge]

Welcome
I'm having a problem with

When I disconnect the 2 brown wires going from the coil to the shift interrupt switch it does not.

Should be one brown going to interruptor
Other goes to the Tach

The interruptor has nothing to do with the trim pump

 

[Scott06]

I only have a gen 2 trim wiring diagram but it looks like there is a 20 fuse in the red between where it takes power off the solenoids and supplies it to the trim/trailer switches at helm and trim limit switch. Weather it was there originally or someone added a newer fuse holder to replace an old damaged one, makes sense that its there.

If it is in the red power line from battery to solenoids that is a different story. That should have a 110 amp cube fuse at the solenoids. Given the difference in wire size I doubt its spliced into the supply line from battery ...

 

[stresspoint]

here you go

 

[MISS demeanor]

@alldodge
"The interruptor has nothing to do with the trim pump"

Hi. I acquired a 78 Bayliner, Mercruiser 120 with several wiring issues. The first one I'm trying to resolve is the trim. On the red wire to the sending unit (pump) a 20 amp fuse has been spliced in and that keeps blowing. When I disconnect the 2 brown wires going from the coil to the shift interrupt switch it does not. I used to have a 78 Baron (predecessor to Power Play) with a 260 in it 20 years ago, and I did most of the work on it myself, but I'm finding my memory a little foggy as to what's what. Is that spliced fuse necessary?

(by sending unit I mean the hydraulic pump that operates the outdrive)

Agreed. And therein lies my question:
connected - fuse blows
disconnected - fuse intact.

 

[MISS demeanor]

@alldodge
The interruptor has nothing to do with the trim pump
Agreed. And therein lies my question:
connected - fuse blows
disconnected - fuse intact.

 

[alldodge]

@alldodge
"The interruptor has nothing to do with the trim pump"


Agreed. And therein lies my question:
connected - fuse blows
disconnected - fuse intact.

Something is miswired.
The brown wire should have no connection to the trim pump

 

[alldodge]

I'm not able to zoom in on pic so not clear of all the connections

 

[MISS demeanor]

Something is miswired.
The brown wire should have no connection to the trim pump

You guys are going to think "she won't get that boat running, she can't even post to the forum correctly!"

How in the hell do I just POST without the past comments being included?

 

[MISS demeanor]

Sorry - I just figured out I was quoting
Let me get some better pictures

 

[alldodge]

Being a 1978 and seeing one relay the wiring should be like this


There should be no connection between the top larger terminals (Red and Blue in pic)


I see a fuse across those and that should not be there (was able to enlarge)

You guys are going to think "she won't get that boat running, she can't even post to the forum correctly!"

No that is not happening

 

[MISS demeanor]

the red wire comes from the boot/harness to the back of the solenoid. They cut that and it becomes (spliced at blue connector shown) they've rigged in a 20a fuse and circles back to solenoid pos post. (Green wire in pic is not connected to red, it goes to terminal block) Also on pos terminal is a wire connecting to pos on coil. (wire is black on L sd of pic facing up.

 

[MISS demeanor]

So on that pos post I've got one to the starter, one to the coil, and (basically) one from the controller with a fuse before

 

[stresspoint]

you're welcome !.

 

[nola mike]

WTF. That makes no sense. LMK if I have this correct:
9 o'clock position: 1. Main (+) connection to battery/starter--always hot (no 110a fuse on the early ones? 2. Wire to coil pos--always hot? 3. Fused link to 3 o'clock position
12 o'clock: grounds
3 o'clock: 1. Fused link from 9 o'clock 2. red wire to control switch 3. Blue wire to trim pump
6 o'clock: blue wire to control switch

If that's how it's wired, then: 1. Ignition is always powered, boat won't shut off, 2. 3 o'clock is always hot, trim motor is always running.
Something must be altered elsewhere as well.

Edit: Also, those 2 wires to the shift interrupt switch. Where are they coming from (should be coil neg, but only 1 wire)? Both connected to the same side of the switch?

 

[alldodge]

Also on pos terminal is a wire connecting to pos on coil. (wire is black on L sd of pic facing up.

This would keep power to the coil even with key off, needs to be removed

Suggest remove every wire that is not in the drawing.

 

[04fxdwgi25]

needs to be rewired per @alldodge's diagram.