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Author Topic:   1974 Boston Whaler Montauk Wiring Diagram
gkamanao posted 09-03-2009 02:26 AM ET (US)   Profile for gkamanao   Send Email to gkamanao  
I have a 1974 Boston Whaler Montauk and I am had to do all the rewiring, could someone steer me in the right direction to finding the wiring diagram for this boat. I apparently am having some difficulties with the wiring. So far I have hooked up the bilge pump, navlights and the fish finder. The power to the boat is not a problem, the problem is the Tach, temperature gauge, heat guage and the hourly meter. If someone could find a picture of the layout, I would be happy. Better yet, If I can find a old owners manuel, I would gladly pay for it.


number9 posted 09-03-2009 03:02 AM ET (US)     Profile for number9  Send Email to number9     
All of the mentioned gauges should be wired according to the currently installed motor manufacturer's recommendations. Usually there are wires or plugs on the control end of the motor harness. There is information in the reference section on color codes used.
Phil T posted 09-03-2009 07:18 AM ET (US)     Profile for Phil T  Send Email to Phil T     
Glen -

There was no set wiring setup for Boston Whaler's untill the late 90's since the motors were rigged by the dealer.

Once Boston Whaler started selling hulls with Mercury outboards, they designed a standard rigging proceedure and had a wiring diagram.

What brand of engine and gauges do you have?

Here is a list of the various color codes for wiring:

I suggest you write out a wiring diagram (noting colors) for everything you have. It does not have to be pretty, just accurate.

Post questions.

P.S. = I have done two re-wires; 1987 Montauk and 1991 Outrage 17)

jimh posted 09-05-2009 06:05 AM ET (US)     Profile for jimh  Send Email to jimh     
There are several substantial problems in complying with your request for a wiring diagram for a 1974 Boston Whaler MONTAUK:

--there probably was never an original wiring diagram provided by Boston Whaler with the boat;

--there is no guarantee that the boat's current wiring is in the precise state as when it left the factory;

--the wiring of the engine electrical harness and instrument gauges was not provided by Boston Whaler in 1974, but rather by the dealer who installed the motor.

Older boats tend to have many modifications to their wiring from dealer or owner-added items. I second the suggestion to make a schematic diagram of what currently exists on the boat before disassembling anything.

The 12-volt electrical system on a boat is quite simple. So simple that I will try to describe it in a narrative form, which generally is impossible with any electrical circuitry. Usually a schematic diagram is needed.

A battery is connected to a primary power distribution system consisting of a disconnect in the positive lead and two heavy distribution buses, one for positive and one for negative.

The outboard motor is directly connected to the primary power distribution.

A secondary power distribution is connected via a current protection device, either a fuse or circuit breaker in the positive lead, to the primary power power distribution buses.

The secondary power distribution generally provides a number of outlets with individual current protection, either fuse or circuit breaker, for each branch circuit. A common negative bus is provided.

All vessel electrical loads such as lamps, blowers, accessory electronics, and so on, are connected to the secondary power distribution panel. If there are control switches, install them in the positive lead.

jimh posted 09-05-2009 06:09 AM ET (US)     Profile for jimh  Send Email to jimh     
There are many suppliers of marine electrical wiring accessories for primary and secondary power distribution on a small boat. The accessories generally come with wiring and installation suggestions. A good source of such accessories is the BLUE SEAS line of electrical products. Their website has a great deal of technical literature which can be obtained for free that will give you guidance in use of their products. See:

gkamanao posted 09-15-2009 05:55 PM ET (US)     Profile for gkamanao  Send Email to gkamanao     
Everyone thank you for your input. I wired all my electronics: GPS, Fishfinder,Bilge Pump, Running Lights and Compus and they all work great. My only things left to do is the OMC RPM guage, temp gauge and hour count gauge. The harness from the motor is my que, so I will be very careful and try to figure this one out. Once I get this done then I am safe to say, it's alright. Again, everyone, thanks for your input. I am still trying to find a photo on the wiring from the engine to the guages.
jimh posted 09-19-2009 12:13 PM ET (US)     Profile for jimh  Send Email to jimh     
For general advice on electrical installations on a small boat, see my article in the REFERENCE section:

Boat Electrical Circuits and Wiring Practices

This will give you a good foundation for installation of electrical systems on your small boat.

For information about the ignition wiring of OMC motors in particular, see my article in the REFERENCE section:

Ignition Switch Wiring

Connecting an OMC tachometer is extremely simple. The tachometer typically has a integral cable with connector that mates to a corresponding connector provided on the engine remote controls. This is diagramed in the article I mention above. By reference to this diagram and knowledge of wiring color codes you can also install an after-market tachometer which lacks the connector. The usual arrangement of terminals on a tachometer is as follows:

I or IGNITION = Violet; switched 12-volts from ignition key
G or GROUND = Black; battery negative
S or SENSOR = Gray; from engine charging circuit

If the gauge has a lighting circuit, it will be marked

L or LAMP = Blue; gauge illumination circuit

gkamanao posted 09-22-2009 03:19 PM ET (US)     Profile for gkamanao  Send Email to gkamanao     
Hey Jimh,

The picture diagram was what I was looking for. Now I can complete the hookup, once I complete this and get things working properly, I will take a picture and post it.

The old wiring was done by someone who was just adding wire without thinking. They either were incorrect or was just hanging down from the bus board.

Everyone, thank you for your kind expertise.

Glen from Hawaii

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