79 Mercruiser 5.7 wiring help !

[jons79searay]

I'm new to boats and I'm trying to do a lot of maintenance and upgrades myself. It's tough when info is limited but It's a challenge and after it's done and fixed, It's satisfying. Well I'm definitely not at that stage yet. LOL

Does anyone have a good diagram of the merc 5.7L wiring? I have found a few and I'm trying to wade through this and fix my problem.

Background....

When I purchased the boat last season, I knew it needed some work to get it up to speed. In the most part everything worked and I am in the stage of upgrading now. I fabbed a new aluminum dash and remounted all gauges, did a total rewire of the motor and accessories, and upgraded to an auto flat fuse system instead of the barrel fuses. It took some time but I'm almost finished. I have now rewired something wrong and can't figure out where I went wrong. I had no problems starting and running the motor before the wire "upgrade" but now it won't start. I will crank but not catch and run. I am getting spark from the cap, and fuel when I manually pump the throttle but I think I'm not getting fuel to run? Please throw out some suggestions on where to start to look and possible solutions.

_________________________________________________

OK, I went out and cleaned up and did some re-routing of the wires and labeled them. It ran two weeks ago when I last ran it with no problems. I touched nothing at the engine side of things. I probably missed or wired something wrong.

After doing some investigating, this is what I found....

Plug 1 / 8-pin
____________________________________
1) Black-------------------Ground
2) Blue--------------------Cuddy cabin lights
3) Brown/white-stripe------Step Down Pump
4) White------------------Stern Running Lights
5) Brown------------------Auto/bilge pump
6) Yellow------------------Blower at Motor
7) Brown------------------Run/Bilge pump
8) Black-------------------Ground


Plug 2 / 6-pin
______________________________________
1) White------------------Port run light
2) White------------------Stb run light
3) Orange/blue-stripe------Horn
4) Grey/Red-stripe---------Bow run light
5) Black-------------------Ground
6) Black-------------------Ground

Main wire Harness
______________________________________
1) Black-------------------Ground
2) Brown------------------Sender to Tach to tach
3) Green------------------Sender to Water Temp
4) Red/White-stripe--------Sender to Amp Meter
5) White------------------12V to Key-switch Acc/Run
6) Red---------------------Constant 12V
7) Yellow------------------12V to solenoid when starting
Goes through Neutral interlock switch in your control.
8) Orange------------------Sender for Oil Pressure
10) Purple------------------Sender for Trim/Tilt

I have wired all Nav Lights in the gauges in with the running/nav lights to a separate switch.

*****I seem to have found the Problem!!!*****
I found 2 wires not hooked up. 1black and 1white wire going to the shifter control. Not sure what this is????? The Neutral interlock worked when this was not powered up. I'm assuming that black is ground and white would be either Accessory power or constant power. I'm guessing accessory power.


Yellow out of the harness to white and black is back to the yellow hooked up to accessory power ?

Is this right?

 

[helms1200]

From what I have been told the shifter control will kill the motor slightly to shift into forward and reverse. But its not enough for you to notice. And if it not right the boat will not run.

 

[jons79searay]

OK, Now I'm chasing electrical gremlins.

I fixed the no start problem and verooooommmm, it started right up.
Now my trim tilt is not working. I don't know????My question is I have
power to the pump through the solenoids down to the wire harness.
From there the 4 wires go up to the trigger switch on the throttle. I'm
not sure if the problem is in the switch or not. I'm going to bypass the
switch and use a jumper from the red to blue or red to green to see if
the pump operates. if so, I have a bad switch and I'll probably mount
a new on on the dash and bypass the trigger switch on the throttle. If
not I have to start troubleshooting the T/T pump itself.

What does the purple wire do on the 4 wire set up from the throttle to
the T/T pump?
There is......
__________________
Green is the down
Blue is the up
Red is the power
Purple is ?????

The purple wire is not hooked up to anything back by the T/T pump.
What is this for?????

 

[jons79searay]

I think the 2 blue wires tied together and the purple wire are high and low limit switches for the trim/tilt. I have trim tabs also. So once I get the motor where I want it, I would use the Trim Tabs more often.

Just did some more troubleshooting and found that from the 3 prong plug up to the switch on the throttle, is open. I have no power going to the switch.

I stripped the wires out of the throttle and pulled the extra 10ft of wire up to a 2 position switch on the dash. I rewired the blue green to the top and bottom of the switch and made a jumper from my positive lead that's always hot on the Amp gauge to the center of the switch. This was to prevent from running 30ft of wire to energize the switch.

It never had the up or down limit switch wired in. Now I know what it is and how it's wired, I will start the search to locate them and replace the limit switches and sending unit.

Another project, Another day !!!!

John

 

[Tail Chaser 661]

You sure picked a hard color to trace :smt013
Looking at bits and pieces of the 1985 schematics

You have purple powering all your gauges and going to your ignition switch B term.
Looks like theres a purple jumper wire on the two up connectors on the power trim control (Page is torn)

You also have purple from the Ignition amplifier to the pos coil term. And another purple from the pos coil that splices to a purple alternator wire. I'm guessing the purple alternator wire is the same purple that powers the gauges and is also attached to the key ignition B term
It goes through the 10P connector
Hope this helps :smt101

I see your engines running now. But theres no trim.
My pump has a 20 amp inline fuse. There's also a 110 amp fuse thats wired directly from the battery.
Looks like the sytem has three fuses to check. There one at the trim control also

 

[jons79searay]

WoW! I found the exact schematic of all wiring to my motor and all accessories. The purple and blue wire go to the trim up limit switch to prevent trimming up to far while under way and separating from the gimble bearing flare. A brown/white wire is spliced to a solid purple that goes to the trim sender.

 

[AKBASSKING]

You can also call Mercury with your engine serial numbers and then you can order your service manuals

 

[jons79searay]

I found these schematics of the wiring diagrams of the Mercruiser 5.7L wire harness
and gauges. I thought I would share them for everyone to use.

I did solve my problems and figure out what all the "wires" were and the only thing I have
left to wire up is the trim sender to the gauge and the high limit switch. Both sets of wires
are there and wired through the hull but are corroded off and I have to run new jumpers to
see if they even work. Another time. I want to get in the water for the first time this year
on Friday. I will be careful with the trimming of the outdrive. I also have Trim Tabs and now
have them working for the first time.

Thanks and Enjoy,

John

 

[chuckvm]

where is that 20amp fuse located in the boat ? i can't find it and think that is why my boat won't start either.

 

[jons79searay]

Mine didn't have one so I put one in. It is an in line auto flat fuse type
you splice in. The cost about 5.00 at the local auto parts store. It's
supposed to be in between your key switch and your amp meter. If yours
is not there, it might be up under the dash by the gauges. You have to
unscrew the panel or I'm my case lift the hatch door to access the wiring.

Hope this helps !

John

 

[Jeanne]

You sure picked a hard color to trace :smt013
Looking at bits and pieces of the 1985 schematics

You have purple powering all your gauges and going to your ignition switch B term.
Looks like theres a purple jumper wire on the two up connectors on the power trim control (Page is torn)

You also have purple from the Ignition amplifier to the pos coil term. And another purple from the pos coil that splices to a purple alternator wire. I'm guessing the purple alternator wire is the same purple that powers the gauges and is also attached to the key ignition B term
It goes through the 10P connector
Hope this helps :smt101

I see your engines running now. But theres no trim.
My pump has a 20 amp inline fuse. There's also a 110 amp fuse thats wired directly from the battery.
Looks like the sytem has three fuses to check. There one at the trim control also

You sure picked a hard color to trace :smt013
Looking at bits and pieces of the 1985 schematics

You have purple powering all your gauges and going to your ignition switch B term.
Looks like theres a purple jumper wire on the two up connectors on the power trim control (Page is torn)

You also have purple from the Ignition amplifier to the pos coil term. And another purple from the pos coil that splices to a purple alternator wire. I'm guessing the purple alternator wire is the same purple that powers the gauges and is also attached to the key ignition B term
It goes through the 10P connector
Hope this helps :smt101

I see your engines running now. But theres no trim.
My pump has a 20 amp inline fuse. There's also a 110 amp fuse thats wired directly from the battery.
Looks like the sytem has three fuses to check. There one at the trim control also

I am new to the board and saw you have the manual to my 1985 sea ray. Do you have the wiring diagram for the 1985? I bought the boat last year and it had a new motor put in with 60 hrs it. The guy couldn't get it to turn over and thought it was froze. I changed the fuel separator, plugs, coil, distributer, cap , wires, 2 new batteries, starter sylanoid, and ignition. I've been chasing wires left and right. I could really use the dash wiring diagram please.

 

[Lazy Daze]

I am new to the board and saw you have the manual to my 1985 sea ray. Do you have the wiring diagram for the 1985? I bought the boat last year and it had a new motor put in with 60 hrs it. The guy couldn't get it to turn over and thought it was froze. I changed the fuel separator, plugs, coil, distributer, cap , wires, 2 new batteries, starter sylanoid, and ignition. I've been chasing wires left and right. I could really use the dash wiring diagram please.

Your owner's manual should have this info. If you don't have it, download it from Sea Ray's website. On the other hand, dash wiring is pretty much the same from one boat to another and even 5 years one way or the other likely won't matter. For example, in your style boat (whether bowrider, Weekender, Sundancer), ignition wiring... gauges... all the same.

 

[Jeanne]

Your owner's manual should have this info. If you don't have it, download it from Sea Ray's website. On the other hand, dash wiring is pretty much the same from one boat to another and even 5 years one way or the other likely won't matter. For example, in your style boat (whether bowrider, Weekender, Sundancer), ignition wiring... gauges... all the same.

Thank you so much I will look that information up on different years. I went to the archives of searay for the manual and before 89' they don't have them. I called my sea ray dealer last Thursday and he's been trying to find my manual. Again ty for the help.

 

[Lazy Daze]

I went to the archives of searay for the manual and before 89' they don't have them.

You may have missed it? It's there. I know they have them going back much earlier, still.

Just checked... they have it.

 

[NorCal Boater]

The American Boat & Yacht Council (ABYC) established a 12 volt wiring color protocol many years ago and most boat manufacturers conform to this color coding. I have been restoring a 1985 Cobalt 23' and the wire color coding is the same as on every boat I've owned or worked on. Mercruiser also conforms to this code in their wire harnesses. Take a look at this link https://www.defender.com/pdf/abyc-wire-color-chart.pdf This is the code I described.

You don't really need the Sea Ray diagram as the ABYC wiring code is uniform to most all boats. If you do an online search for "ABYC Wire Color Code" you will find countless boat wiring diagrams. I have almost completely re-wired my Cobalt and have purchased the wire I needed from vendors on eBay.
Shawn

 

[Neil Goldberg]

OK, Now I'm chasing electrical gremlins.

I fixed the no start problem and verooooommmm, it started right up.
Now my trim tilt is not working. I don't know????My question is I have
power to the pump through the solenoids down to the wire harness.
From there the 4 wires go up to the trigger switch on the throttle. I'm
not sure if the problem is in the switch or not. I'm going to bypass the
switch and use a jumper from the red to blue or red to green to see if
the pump operates. if so, I have a bad switch and I'll probably mount
a new on on the dash and bypass the trigger switch on the throttle. If
not I have to start troubleshooting the T/T pump itself.

What does the purple wire do on the 4 wire set up from the throttle to
the T/T pump?
There is......
__________________
Green is the down
Blue is the up
Red is the power
Purple is ?????

The purple wire is not hooked up to anything back by the T/T pump.
What is this for?????

 

[Neil Goldberg]

It for the trailering mode. It basically uses a separate switch and ties into the blue wires that cause the outdrive to tilt up. It's really a non feature because the trailering switches don't allow you to move the drives down. You have to use the normal trim switches for that. I'm not going to be trailering a 6 ton boat with ANY regularity.

 

[techmitch]

It for the trailering mode. It basically uses a separate switch and ties into the blue wires that cause the outdrive to tilt up. It's really a non feature because the trailering switches don't allow you to move the drives down. You have to use the normal trim switches for that. I'm not going to be trailering a 6 ton boat with ANY regularity.

You do realize this thread is over 2 years old?

 

[Neil Goldberg]

You do realize this thread is over 2 years old?

Yes, but the question remains relevant. I figured this out while changing my control binnacle and control cables. I'm trying to contribute helpful info since the forum is searchable