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Use of Electronic Test Equipment


********      This information is supplied as a service guide only and Outboardparts.com is not liable for any misunderstandings, errors or omissions regarding this information. The information has been obtained from actual Unit analysis, parts manuals, and other sources.      ********

The purpose of this brochure is to give the marine technician a general overview or the types of test equipment and their use.  The most common, easy to use, test equipment will be covered.
Due to the rapid development of computerized EFI (Electronic Fuel Injection) and ECU Ignition systems, more complicated and expensive test equipment will be developed for the marine industry, just as it has been developed for the automotive industry. Some newer equipment will include the use of scope meters (such as the Fluke 98), ECU and EFI testers, digital analyzers, and computer interface testers. Hopefully, the newer test equipment will be user friendly and many troubleshooting problems will be diagnosed with less complicated equipment.
The test procedures at the end of this brochure are intended to give the technician a better understanding of the most common failures and allow testing with minimal equipment.

Test Equipment and Measurements  

I. VOM (Volt-Ohm-Meter) Multimeter

A. Analog meter - The analog VOM is a dial/needle movement with multiple switch settings

       and ranges on each setting. This meter usually requires "calibrating" of the scale before use.
       They normally consume batteries at a fast rate.
B. Digital meter - The digital VOM uses a digital display to indicate the readings. Of the
       following types, the manual and autoranging are the most popular:
       1. Manual range setting - The measurement range is selected by a switch, i.e. 20 ohm,
              200 ohm, 2k ohm, 200k ohm and 20M ohm.  The symbol for ohms is W.
       2. Autoranging - A true autoranging meter will automatically select the correct range for
              the measurement being taken, i.e., you can measure 20 ohms and 2k ohms without
              changing anything on the meter.  The Type of measurement still has to be manually 
              selected, i.e., AC Volts, DC Volts, Ohms, AC Amps and DC Amps. 
       3. Manual / Autoranging - Some meters have both manual and automatic settings, i.e.,
              the Fluke 88, Fluke 29, etc.
       4. Ranges - As a reminder, when referring to electronics, the k is 1000, i.e., 1k ohm is
              1000 ohms and 20k ohms is 20,000 ohms.  The M is 1,000,000 i.e., 2M ohm is
              2,000,000 ohms.
II. Peak Reading Voltage Measurement
       A. DVA (Peak Reading) Voltmeters - Specialty meters for measuring average DC
              voltages and AC voltage spikes on Ignition systems. Some of the more common
              meters include the Stevens CD-77, Merc-o-tronic and ESI meters with DVA ranges.
       B. Multi-use Voltmeters with DVA Adapters - Analog or digital VOM (volt, ohm
              meters) using a plug-in DVA adapter to measure DVA voltages. Accuracy varies 
              quite a bit between manufacturers and types of meters when taking DVA readings.
              The CDI/Rapair 511-9773 peak adapter is highly recommended for use with all
              Fluke meters.
III. RPM (Tachometer) Measurements
      A. Inductive Tach Measurements - This type measurement is made by clamping a
inductive pickup probe on one of the spark plug wires. Very few of the inductive systems will work well on two cycle CD ignitions due to the RF and microwave noise being generated. The Fluke 88 Multimeter used with the CDI/Rapair 511-9788B two cycle adapter, is highly recommended.  The  Merc-o-Tronic Inductive Tach and the CDI/Rapair  Tach Adapter (P/N 511-9785) are some of the units recommended for both two and four cycle service.  Inductive tachometers can be a real time-saver when trying to find a high speed miss by comparing the readings on all cylinders, i.e., if one or two cylinders shows a big difference in comparison to the other cylinders. The use of inductive tachometers is recommended for detection of double firing cylinders. If one cylinder shows twice the RPM of the other cylinders, it is probably double firing.
      B. Reflective Tach Measurements - These are optical tachometers, that use a piece of
reflective tape on the flywheel or pulley.
      C. Contact Tachometer - NOT RECOMMENDED for Outboard Use.
Uses a center hub rotator and counts the RPM..
      D. Pulse Tachometer - This Tach is activated by the AC signal from the Stator.  The
RPM signal is related to the number of Pulses received from the Stator.
IV. Temperature Measurements
      A. Thermocouple / Meter System - This is probably one of the most useful systems.
The Fluke 51 and 52 temperature meters, or the accessory temperature attachments for the Fluke meters, are capable of measuring exhaust gas temperature, water temperature, head and block temperature. Various probes are available for different types of measurement with the bead probe being one of the most useful. The bead probe can be positioned on the block with the use of duct tape.
      B. Infrared Temperature Probes - They can be used to measure temperature at various
points on the engine or water temperature without contact. However, some running engines generate too much electronic static and will interfere with the infrared sensor readings.  Holding the temperature probe too close may cause the Ignition noise to ruin the Unit.
      C. Temperature Sticks, Paint or Labels - These can be used for quick measurement
of over heating conditions.
V. Pulse Measurements / Frequency Measurements
This is a good method to check electronic fuel injection systems (EFI). A measurement of the injector Pulses at a set RPM can determine if the injection system is performing properly.  At the current time there are few recorded measurements on the various EFI systems. The Fluke 88 meter is one of the meters designed to measure EFI Pulse rates.   
VI. Resistance Measurements 
This is one of the first and easiest measurements that needs to  be taken on an Ignition system.  The charts in the back of this brochure are furnished as a guide.  Be aware that temperature can make a slight difference in the readings. The higher the temperature - the higher the resistance reading is going to be. One final note, a Stator or Trigger can test fine with an ohmmeter and still be bad.     
VII. Current Measurements
      A. Direct Volt Amps (DVA) - One of the most important measurements to be taken on
Ignition systems are voltage measurements using a DVA meter, or peak reading (DVA) adapter with a good VOM. The Fluke *a Kit is highly recommended by out Technical Service Department. The charts in the back of this brochure give the readings for a majority of the engines. On an engine with a split Ignition, if only one side fires, compare the readings between the sides. Typically, the DVA readings for Yamaha and Suzuki will be close to that of Mercury Outboard. A simple test on rectifier/regulators (except OMC rectifier/regulators without cooling fins on the bottom) can sometimes be a time-saver. with the engine running at approximately 1200-1500 RPM. DVA test from each yellow Wire to engine ground. The readings should be within 11/2 volts of each other, i.e., if one Wire reads 20 volts - the other has to read between 18 1/2 and 21 1/2 volts.  If one Wire reads low, mark the Stator and rectifier Wire with the low reading, shut the engine down and swap Stator wires. Crank the engine up and repeat the test. Whichever part with the striped Wire that has the low reading is bad. Repeat the test for yellow wires to the red Wire going to the battery / solenoid.  
      B. DC Voltage - Most battery CD Ignition modules are sensitive to low battery voltage 
and battery reversal. During cranking, a DC voltage level at the pack of less than 9 !/2 Volts is unacceptable and indicates a problem in the Harness, keyswitch, starter or battery. WOT voltages above 16 volts will blow most battery ignitions. Problem is likely to be either the battery or cables.
VIII. Current Measurements
This is a good way to check the regulator/rectifier battery charging operation in the charging system. The 10 amp charging system can be checked with a good VOM that has up to 10 amp capability (Fluke 29,73,88, etc.). The red Wire is disconnected from the rectifier, the one meter probe is placed on the connection, and the other is placed on the red Wire.
Warning! Make sure you do not exceed 10 amps or touch ground with one probe. This could damage the meter. The 35 amp charging system requires an inductive pick up or a high current amp adapter, such as CD/Rapair's 511-9772 (1-400 amp). Remember, on outboard charging systems at idle speed the current is @ 1/5 of the current rated.
IX. Battery CD Tester
This is used to test battery CD modules on the engine by replacing the points or triggering device electronically. The CDI 511-9701 Battery CD Tester is highly recommended due to its ability to fire the Ignition systems up to 3000 RPM without the engine running. It can be used to test the CD module, distributor cap, Ignition coil and plug wires. Additionally, the tester can be used to test Mercury Outboard EFI injectors.
X. EFI Tester
Electronic fuel injection testers are available for use with the specific type of EFI system it was designed for. Use of these testers are not covered in this brochure.
XI. Trigger Tester
A break through by CDI/RAPAIR (511-9710) allows you to test most Mercury Outboard, Mariner, Force Outboard Motor, Chrysler triggers and OMC's Quick Start timer bases on the engine. The Unit can be used to test points, preamp triggers, Mercury Outboard battery CD triggers, hall effect triggers, Alternator driven Ignition triggers, and can be used to check injection Pulse from Mercury Outboard EFI modules.

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