Re: [OMC-Boats] Wiring questions from Ian Torrey on 2009-06-17 (OMC-Boats Mailing List Archive)

From: Ian Torrey <itorrey@...>
Date: Wed, 17 Jun 2009 12:59:35 -0400

Lee, after about 5 years of trying to figure these systems out, you¹ve
finally made this all make sense to me! Hallelujiah! Seems all of the same
theory would apply to my Œ66 OMC 100hp motor I could never quite figure
out what the ³little clay brick² was for even with the repair manual.
Thanks for taking the time to give this detailed overview.

Many thanks,
Ian

On 6/17/09 11:15 AM, "Lee Shuster" <lks@...> wrote:

> JD,
>
> Sometimes electrical terminology gets confused with thermodynamics
> terminology. I'm going to assume when you use the term "HOT" you mean
> thermally, not (necessarily) presence of electrical potential (voltage)
> although it sounds like both may possibly be present.
>
> Let's also clear up some other terms. An engine can be not running, (as in it
> just stalled) while the helm-mounted IGNITION switch is still in the ON
> position. The original OMC Ignition switch has OFF - ON (RUN) - START
> positions.
> Note: Unlike most automotive applications, there is no ACCESSORY position on
> this switch. You can retrofit a new switch if you want to run electronics or
> other devices with the motor not running.
>
> NEVER Leave the IGNITION SWITCH in the ON position when the engine is NOT
> running. The ballast resistor and coil will heat up under normal operating
> conditions, but you risk damage and failure leaving the key ON with the engine
> not running. Also with the switch ON, if your sterndrive was out of water and
> in gear (forward or reverse) additional current would flow to the clutch coils
> and generate excess heat in the lower unit. At the very least you'll
> potentially drain down and discharge a marginal battery and not be able to
> raise or lower your power lift or start your engine. And we know how much
> wives or significant others love that!
>
> I've never taken ballast or coil temp measurements after prolonged (normal)
> usage, but I would imagine they will be quite warm. But here's what's more
> important: The resistor and coil WILL cool off rapidly when you shut the IGN
> SW OFF.
> So do that check, as well as the the other checks I've listed below. There
> should obviously be no voltage present with the IGN SW in the OFF position at
> the coil or ballast resistor.
>
> Here's a couple of factory OMC wiring diagram you can reference (both wired
> identically, just different wiring color schemas depending on age of your
> boat):
>
> http://hhscott.com/evinrude/images/wiring/68_v6_ALL_WIRE.jpg
> http://hhscott.com/evinrude/images/wiring/73_OMC_V8_all_big.jpg
>
> I can't tell from you description if your boat has been re-wired or mis-wired.
> On the POS (+) side of the coil, one (red) wire should trace back to the
> ballast resistor and measure about 6 - 8 volts with the IGN Switch ON. The
> other wire should be RED/WHITE STRIPE and it should run back to the starter
> solenoid. It should measure 12-13 volts only when the SWITCH is in the START
> position.
>
> This additional info may help you/others to better understand why Ballast
> Resistors are sometimes used in Coil-Points Ignition systems.
>
> There are many misconceptions about ballast ignitions and what they do. Up
> until about 1955, most vehicles used 6-volt systems. When the switch was made
> to 12-volt system, higher compression V8 engines were putting greater demands
> on ignition systems. Some bright engineer got the idea that a hotter spark
> could be provided using existing 6-volt coils. The full 12-volts is
> "temporarily" provided for "hotter" staring spark, and then the coil is
> returned to operated on 6 to 8 volts during normal running. The ballast
> resistor is what reduces the 12-14 volts essentially in half. If you know Ohms
> law you do the math.
>
> The ballast ignition system includes an external resistor in series with the
> voltage supply to the coil¹s (+) terminal. A internal resistor coil will have
> an internal resistance close to 3 ohms on its primary windings. The coil for a
> ballast ignition system (As on OEM OMC boats) will have a primary winding
> resistance between 1 and 2 ohms. The external ballast resistor will typically
> provide an additional 1.5 - 2 ohms of resistance.
>
> Current flowing through the ballast resistor will create a voltage drop and
> thus lower the coil¹s operating voltage to something between 6- and 9-volts.
>
> Together, the ballast resistor and the internal resistance of the coil limit
> the current flowing through the system. The coil in a ballast ignition system
> will have a second connection on its (+) terminal. (sometimes these are joined
> on the ballast resistor, rather than the coil) This second connection is from
> the starter solenoid. During cranking the coil¹s (+) terminal will receive
> full battery voltage. This produces a MUCH hotter spark to help the engine
> start. Once the starter is released the coil receives its power through the
> external resistor which drops its operating voltage to the 6 - 9 v range.
>
> The ballast coil can thus produce a hotter spark for starting. However, if the
> ballast coil is wired into the ignition system WITHOUT the external resistor
> it will always operate at high voltage. The increased current flow through the
> system and the higher spark voltages will cause premature failure of the
> distributor points. It is imperative therefore that the proper coil be
> installed to maximize its ignition system reliability and life. When
> troubleshooting a ballasted ignition system the external resistor and its
> associated wiring must be added to the components to examine.
>
> It is important when buying a replacement coil that the correct type is
> selected for the ignition system to achieve acceptable life and performance.
> Old boat ignition systems are often modified over the years and determining
> what is required may not be as simple as referring to the owner¹s or service
> manual. Visual checks should be performed first. Externally ballasted
> ignitions use a ballast resistor between the ignition switch and the coil (+)
> terminal (frequently RED or sometime PURPLE/BALCK in color). The ballast
> resistor will typically appear as a small ceramic brick (with wires) mounted
> in the vicinity of the coil itself and connected between the ignition switch
> and coil (+). Ballast ignition systems also have a wire between the coil (+)
> terminal and the starter solenoid.
>
> If the boat's electrical system is totally unmolested these visual clues may
> be enough to identify the ignition coil type installed/needed.
>
> To confirm the needed coil type it is best to make electrical measurements
> with a volt/ohm meter. Start by measuring the resistance across the coil¹s
> low-tension terminals with all the wires disconnected. Note this resistance
> value but do presume it correctly identifies the coil needed. Perform the
> following additional test: Re-attach the low-tension wires removed to perform
> the previous test. Connect the volt meter between the coil¹s (+) terminal and
> chassis ground. Temporarily fit a jumper wire between coil (-) and ground. The
> jumper wire will insure that current is flowing through the coil and any
> ballast components during the test. It is necessary for current to be flowing
> to correctly measure the coil¹s operating voltage. With the meter and jumper
> wire connected, switch on the ignition and observe the meter. If the meter
> shows battery voltage (nominally 12V), the system is non-ballasted and needs a
> standard (internally ballasted) ignition coil. If the meter displays anything
> between 6V and 9V, a ballast-type ignition coil is required regardless of what
> type of coil is currently on the boat. Internally ballasted ignition coils
> will have a primary resistance close to 3 ohms, while externally ballasted
> ignition coils are typically between 1 ohms and 2 ohms. Using a standard
> (internally ballasted) coil on an externally ballasted ignition system will
> result in low spark voltages potentially leading to running problems. Using a
> ballast-type coil on a standard ignition system (without an external ballast
> resistor) will result in excessive current flowing through the ignition
> system. This will cause premature wear of the points and potentially lead to
> reduced coil life.
>
> Lee Shuster
> Utah
>
>
> On Jun 16, 2009, at 8:47 PM, jd wrote:
>
>> Two different mechanix have messed with my wiring and even though it
>> started/ran yesterday, things don't seem right....
>>
>> 1) what is the ballast resistor for and is it supposed to be 200+ degrees
>> when engine is off/cold? I'm guessing no. Both terminals light up my tester
>> when grounded.
>>
>> 2)is coil supposed to be hot when engine Is off/cold?
>>
>> 3) neg terminal of coil has black from distributor, and grey from tach. Pos
>> terminal of coil has red from distributor and red coming from one of ballast
>> resistor's terminals.
>>
>> Other ballast resistor has purple coming from looks like ignition.
>>
>> Thanks!
>>
>>
>>
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