RE: [omc-boats] Wiring Sub Harnesses

From: Ian Torrey <itorrey@...>
Date: Tue, 14 Jun 2005 11:38:34 -0400

Hi folks. I have a more basic wiring question I was wondering if someone
could help with. My Sweet 16 with vintage 100hp Johnson outboard has more
cables and wires than I know what to do with at the battery terminals, and
no clear indication of what attaches where. So far I've never managed to get
this to turn over since I bought it (I admit that I haven't found a lot of
time for actually experimenting). I presume some of the wires might be for
aftermarket accessories, and would like to just find out what the basic
connections should be just to get the boat running. Anyone know of where I
might get instructions for the basic hookup?
Thanks for all the great posts. I don't say much, but read most of them :)
Ian Torrey
Ottawa, ON

-----Original Message-----
From: owner-omc-boats@... [mailto:owner-omc-boats@...]On
Behalf Of LShuster (lib1)
Sent: Wednesday, June 08, 2005 2:32 PM
To: omc-boats@...
Subject: Re: [omc-boats] Wiring Sub Harnesses

If wiring seems complicated, it sometimes helps to break it down, and to try
& understand what the basic sub-harness functions are. This wiring
schema-design philosophy is fairly common across the entire range of
OMC-powered 4-stroke I/O boats. There are some minor differences between
years and models but they are relatively minor. The 2-stroke V-4's are quite
different on the motors themselves and use a slightly different
motor-to-dash cable assembly from their more common 4-stroke brothers. For
easier service, that dash/switch panels were modularly connected in later
models (pos-'67). 1) Battery Cable Assembly (easiest of all to reproduce)
Red (+) runs from battery to Starter solenoid, Black (-) to engine ground
2) Terminal block (usually 4-post) located in engine area, sometimes there
may also be one under the dash.
3) Fuse Block (located under dash) usually has both pos and neg feed inputs
with 9 fused outputs and ground buss terminals. Uses common "glass-type" AGC
fuses. Fuse/circuit positions are lableled: Spare, Pump, Horn, Cig(ar), WW,
Inst(rument)., Runn(ing), Int(erior) , Spare.
4) Dash Panel Cable Assembly. This cable connects to your instruments,
warning lights, and switch gear or one end. The other end has two large
multiple-pin connectors that hook up to the motor-to-dash cable.
5) Motor-to-Dash Cable Assembly Bow-end connects directly to the ammeter,
while another connector hooks up to electric shift control, two large
connectors hook up to dash panel connectors. Note: on electric stringers
there is no default, "fail-safe" gear engagement system. Make sure your
shifter switch and wiring are working properly. Loss of power to either
forward or reverse coils could ruin your day. On the stern-end there are
two, large connectors: 1) hooks up to engine functions, and 2) connects to
the tilt solenoids and bilge pump/blower. There's typically a stern light
connector and then some heavy, 8 ga wires connect the ammeter to the
terminal block (# above).
6) Tilt/Bilge/Shift Harness/Cable plugs into one of the large connectors
from the motor-to-dash harness. Other ends run to the tilt Up and tilt Down
solenoids, the tilt motor connector, the shifter control harness and the
bilge pump/blower connector.
7) Engine Harness/Cable this also plugs into it's own large connector from
the motor-dash harness. The engine items it is wired to include: Alternator,
regulator, coil, ballast resistor, water temp sensor, oil press sensor,
starter solenoid and starter motor. Don't overlook the separate 8-10 ga
black wire running from engine ground back down to the terminal block
running. It's interesting that that last two cable (#6 and #7) are
considered part of the engine and are not listed in my Sportsman boat parts
book. That probably means that you could pull either of those assembly from
just about any 64 - 77 electric stringer 4-stroke OMC and might
plug-and-play. Chances are it won't be in any better shape than the one in
your boat now, however.
Hope this is helpful. If your want further clarification, take a look at the
wiring diagram(s) that Phil posted and this will make a little more sense.
Sorry my scanner can't do it in one big continous pass.
Lee Shuster
Salt Lake City
----- Original Message -----

From: lib1@... <mailto:lib1@...>
To: omc-boats@... <mailto:omc-boats@...>
Sent: Wednesday, June 08, 2005 8:17 AM
Subject: Re: [omc-boats] Wiring

 Not only can electrical problems be an annoyance (mostly) they can leave
you stranded, or worse, sometimes lead to fires, so this a good topic for
Tom's and Lee's different approaches to fixing wiring harnesses both have
their places. I've done it both ways on a number of cars and boats. Tom's
approach is more time consuming but is ultimately better beacuse with Lee's
approach there's more points of potential failure introduced in the
electrical continuity path. But Lee's approach is more commonly performed by
individuals and shops and can focus on an immediate problem area, typically
with the wiring remaining in the vehicle.
Getting, understanding and verifying the wiring diagrams is essential.
Sometimes on 40-year old technology someone has previously modified a
circuit or used a different color wire. While heat is not the enemy (as it
is in underhood autos) corrison and moisture can and do take a toll on
boats. OMC used to make a tube of electrical connector "grease" that kept
mositure out of the connector and reduced the chance of oxidation or
corrosion. You don't need the OMC stuff, auto parts and electrical supply
places carry it under different names.
One thing I have learned, it's always best to pull the harness completely
out of a vehicle and then lay it out and tag the connectors. This makes it
much easier to measure lengths and to access, inspect and replace connectors
and pins. Take pictures of the connections and make notes before removal if
your unsure of how it all connects. I find I can take my time and do a much
better job on the workbench, rather than curled up under the dash or
reaching under or across a motor.
The process that Tom K. describes can be done at home, but I would add
another tip: Start by practicing on a small sub-section, perhaps involving
something non-critical like nav lights; rather than the tilt or bilge
blower/pump. Also, for anyone that's afraid to do this yourself, I know of a
professional shop (they normally manufacture airbag harnesses) that will
make a completely new vehicle harness, using your old harness as a pattern.
But be prepared to fork over big money to have someone else to it right --
on the order of $900 to $1200 for parts & labor for a complete wiring
Lee Shuster
Salt Lake City

----- Original Message -----
From: Thomas Klauber <mailto:tklauber@...>
To: omc-boats-digest@... <mailto:omc-boats-digest@...>
Sent: Tuesday, June 07, 2005 7:30 PM
Subject: [omc-boats] Wiring

 This message is to all but especially Jay. Here is the way to redo the
wiring harness - it is not the cheapest but is a total redo. First get a
Clymer and a Seloc manual which you really should have already. Find a used
OMC Stern Drive Service Manual for your year and horsepower boat on ebay (
easier said than done but patience will pay off ). You will find wiring
diagrams in all 3 of these publications and each will show the wiring in a
slightly different format but with enough study you can confingure what is
supposed to be on your particular boat. The OMC edition shows the wiring in
color. I have looked forever for used and or new wiring harnesses for the
older boats on ebay and they just dont exist and I did find one used one
that I bought and it was in pretty bad shape but I was able to use the
voltage regulator which you can get aftermarket anyway. Use your old harness
for a template too. Mine was totally toasted. You cut the wires off a little
above the entrance to the plug. There are 2 sizes of pins in the plug. You
work each wire with its pin out the back of the plug through the smaller
hole. The pin is soldered and pressed on the wire end so you will have to
cut off the pressed part - it is impossible really to undo the pressed part.
You do not want to damage the pin cause you are going to re-use it. If the
pin is corroded (like 2 of mine were) then you will have to improvise a new
pin. Dave Losvar at SeaWay Marine in Seattle has the terminals for the other
ends of the wires if you want to get original. He even has the flag
terminals for the temp and oil senders ( for the idiot lights ). He has the
knife terminal disconnects too, otherwise improvise. MAKE SURE YOU USE
MARINE GRADE WIRE AND TERMINALS. You buy Marine Primary Wire from West
Marine which sells the proper grade and color wire to rebuild properly and
they sell it in smaller than 100 ft. spools so you dont have so much left
over. I would not recommend using all one color and grade (unless you are
selling the boat). Remember every connection you put in the harness is a
potential Sunday afternoon breakdown. You will end up buying 10 or so small
spools of wire all different sizes and colors depending on the infomation
you gather from the manual. You get a nice wire stripper and solder the wire
into the pin through the open end which you may have to drill to get inside,
youll see what I mean when you get the pin out and the wire off - the pins
are hollow. You basically are reattaching the new wire to the old pin and
you slide the pin and wire back into the plug. It is not easy to slide the
wire back through the holes left in the rubber plug but if you use the same
size wire as original it will all fit back in place totally like new. I used
a small wire to go through the hole and pulled the wire and plug in from the
front of the plug using a little lubricant. Position the pin back into the
plug the same depth as original. Do this for each wire. When they are all in
then put a little black silicone sealer in the plug end to sort of set the
wires. They can be pulled out again but take a lot of effort and the plug
clamps together and they cummulatively will withstand a lot of pull. You
wrap the harness in harness tape like the original and reinstall. You will
need to measure each wire length carefully so the fit will be proper. Save
stuff like rubber boots and use them again. This is the basics of what I did
and it works well ( so far ). Take your time and measure and remeasure and
check for electrical continuity often. When you are finished you will know
that harness like the back of your hand. It takes a long time but is worth
it. Do it this winter. Take the warness off when you put the boat up and get
to work.Take lots of notes. A temporary fix is to put liquid electrical tape
on the wires to stabilize and insulate them. Once the insulation falls off
they will corrode and fall apart. West Marine also sells Liquid Elec. Tape.
Good luck - hope this helps. TK

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Received on Tuesday, 14 June 2005

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