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Troubleshooting Teleflex Tachometer Gauges




Technical Reference Manual




Tachometers (Diesel)






Tachometer Guide (Diesel)


Diesel tachs may require a sender, depending on the engine. These tachs are offered in "dedicated" (specific sender type) versions. Diesel Tach/Hourmeters are offered in a "programmable" versions (Heavy Duty) which accommodate several sender types or "dedicated" versions (Lido Pro).


1. Engine has No Provision for Tach Sender:

Use Diesel Alternator Tachometer (CODE "T"). Diesel Alternator tachs read the alternator signal. Alternator must have an AC tap, usually marked "AC", "R" or "W". If there's no tap, a local alternator repair shop can usually add one at a small cost. You need to know the number of magnetic poles in your alternator. Consult the alternator maker or local alternator repair shop if in doubt. Also, calculate the pulley ratio from crankshaft to alternator. Determine Switch Setting, based on Number of Alternator Poles and Crank shaft-to-Alternator Pulley Ratio, calculated as follows:

Crank Pulley Dia. / Alternator Pulley Dia. = Pulley Ratio

(Match number of poles and pulley ratio to the appropriate switch position setting on the chart below.)



NOTE: Tachometers are factory calibrated for several combinations of poles and pulley ratios, but in almost all cases you will need a Portable Master Shop Tachometer for initial calibration. Detailed calibration and adjustment procedures are documented in instructions included with Teleflex tachometers.


Programmable Tachometer/Hourmeter: To determine if programmable tachometer is suitable for the application, calculate Full Scale Frequency (FSF) as follows:

# Alternator Poles X Pulley Ratio X 33.33 = FSF (Hz).

(If F.S.F. is 1248 Hz or less, use Low Frequency model Programmable Tach/Hourmeter; if over 1248 Hz, use Diesel Alternator Tachometer.)


2. Engine has Magnetic Proximity Sender Mount:

Use Diesel Magnetic Pickup Tach with Magnetic Pickup Sender (CODE "B"). The sender mounts in a 3/4-16 threaded hole, usually in the bell housing. As each gear tooth passes the sender, a pulse signal is generated. Works with 90 to 180 teeth on gear. (The frequency is too high to allow use of the "Programmable Tach/Hourmeter".)




3. Engine has a Takeoff for a Mechanical Tachometer Cable

Use Diesel Signaflex Tach with Signaflex Sender (CODE "A"). The Signaflex sender mounts in place of a tachometer cable. Select the drive tang that fits the engagement hole. (The Programmable Tach/ Hourmeter may be used in this application.)




Tach & Tach/Hourmeter (Diesel Alternator Type)


(For Diesel or Low-RPM Inboard and Stern Drive Engines:)

  1. For this type of tachometer, the engine is usually a diesel, but can be a low-RPM gasoline stern drive or inboard.
  2. Check all wire connections to see that they're tight and not corroded. NOTE: Some older style tachometers operate with only Ground and Sender connections. Teleflex tachs must have 12 VDC (from the ignition switch, "ON" when engine is running) to the "IGN" stud.
  3. When tachometer is first turned on, pointer must go to zero 50 RPM. If not, check connections (if OK, tachometer is probably faulty).
  4. Voltages with engine running should be: IGN to GND terminal: 12 VDC minimum; SEND to GND terminal: 5 VAC minimum.
  5. Arrow on rotary selector switch must be pointed directly at setting or the tachometer will go to full scale.
  6. Some alternators do not have output terminal for tachometer signal. A local alternator repair shop can install a tap from the internal rectifier to facilitate a tachometer signal from the alternator.
  7. If the number of alternator poles is not known, measure actual RPM with a Master Tachometer. Rotate tach selector switch to the letter that puts the tach closest to actual RPM. Final calibration adjustment requires a Remote Master Tachometer. Connect the master tach and start the engine. At about 1,500-2,000 RPM, use a jeweller's screw driver to carefully adjust the potentiometer in the "CAL" hole (about 10 o'clock on the rear of the tach), bringing the tachometer into agreement with the Master Tach. Only a minimal amount of turning is required. Overtorquing of adjustment will damage gauge mechanism. Turning clockwise increases tach reading, counter clockwise reduces reading. If the tach cannot be brought into calibration, the black Range Selector Switch is probably on the wrong setting.
  8. Alternator belt slippage will cause some error on the tachometer.
  9. Dual stations: the send er will drive two tachometers. Simply connect "IGN" to "IGN", "GND"to "GND", etc. NOTE: mixing brands/ types (such as 2-wire/3-wire, see paragraph 2 above) may cause problems.





Tachometer (Magnetic Pickup) (Code B)

(For Diesel or Gas Engines with a Sender Mounting Point in Bell Housing or Adjacent to a Rotating Gear:)

  1. This tachometer is for a diesel or gasoline engine having a sender mounting point (3/4-16 thread) in the bell housing (or adjacent to some other rotating gear), and 12-16 VDC (24 Volt systems can be accommodated with a Voltage Reducer).
  2. Check all wire connections to see that they're tight and not corroded. NOTE: Some older style tachometers operate with only Ground and Sender connections. Teleflex tachs must have 12 VDC (from the ignition switch, "ON" when engine is running) to the "IGN" stud.
  3. When tachometer is first turned on, pointer must go to zero 50 RPM. If not, check connections (if OK, tachometer is probably faulty).
  4. Voltages with engine running should be: IGN to GND terminal: 12-16 VDC. SEND to GND terminal: 0.3 VAC minimum at idle; (voltage will increase with engine speed).
  5. Set rotary switch on tachometer back to the range that includes the number of gear teeth that pass by the Magnetic Pickup in one crank shaft revolution. This information can be obtained from the Engine Distributor or Dealer. Arrow on slot must point to setting; if it is between settings, the tach will go full scale when engine is started.
  6. Final calibration requires a Remote Master Tachometer. Connect Master Tach and start engine. At about 1,500-2,000 RPM, use a jeweller's screwdriver to carefully adjust the potentiometer in the "CAL" hole (about 10 o'clock on the rear of the tach), bringing the tachometer into agreement with the Master Tach. Only a minimal turning is required. Overtorquing of adjustment will damage gauge mechanism. Turning clockwise increases tach reading, counter clock wise reduces reading. If the tachometer cannot be brought into calibration, the black Range Selector Switch is probably on the wrong setting.
  7. The end of the sender must be within 1/32" -1/16" of the gear teeth, but not touching the teeth. To adjust, stop engine, loosen the lock nut, and gently turn the sender clockwise until it touches the flywheel. Back off (counterclockwise) one turn, and secure with the locknut.
  8. Rust buildup between the teeth can cause signal loss from the sender.
  9. Dual stations: the sender will drive two tachometers. Simply connect "IGN" to "IGN", "GND" to "GND", etc. NOTE: mixing brands/ types (such as 2-wire/3-wire, see para graph 2 above) may cause problems.




Tachometer Signaflex (Code A)

(For Engines which have a Mounting Point for a Mechanical Tach Cable.)

  1. This tachometer is for a diesel or gasoline engine with a tachometer drive cable mounting point, and 12-16 VDC (24 Volt systems can be accommodated with a Voltage Reducer).
  2. Check wire connections. NOTE: Some older style tachs operate with only Ground and Sender connections. Teleflex tachs must have 12 VDC (from ignition switch, "ON" when engine is running) to "IGN"stud.
  3. When tachometer is first turned on, pointer must go to zero 50 RPM. If not, check connections (if OK, tachometer is probably faulty).
  4. Voltages with engine running should be: IGN to GND terminal: 12-16 VDC. SEND to GND terminal: 0.3 VAC minimum at idle; (voltage will increase with engine speed).
  5. Rotary switch on tachometer back must be set to corresponding engine takeoff ratio (takeoff revolutions vs. crankshaft revolutions). This information can be obtained from the Engine Distributor or Dealer. Arrow on slot must point to setting; if between settings, tach will go full scale when engine is running.
  6. Sender is made for engines with a round drive tang fitting and keyway (some engines have a .104 square tang fitting). It will not fit slotted keyway drives. Mounting point threads must be 7/8-18.
  7. The sender produces 8 pulses per revolution.
  8. Drive tang must be properly inserted in both sender and takeoff, and rotating internally. Tang must not be broken, worn, or rounded. At about 1,000 RPM, sender should put out 6 volts peakto- peak (AC sine wave) with tach disconnected.
  9. Dual stations: the send er will drive two tachometers. Simply connect "IGN" to "IGN", "GND" to "GND", etc. Note: mixing brands/types (such as 2-wire/3-wire, see paragraph 2 above) may cause problems.



Tachometer Guide (Gas Inboard, Stern Drive)


Teleflex 6K, 7K or 8K RPM Tachometers and Tachometer/Hourmeters are suitable for use with gas engines with fac to ry-installed ignition systems, except: 1960's vintage Mercruisers with Thunder bolt I ignition, and Indmar LT-1 engines.

Rotary selector switch on rear of tachometer must be set to number of cylinders in the engine: 4 cylinder = 4C, 6 cylinder = 6C, 8 cylinder = 8C

Note: Teleflex has not tested the various aftermarket bolt-on ignition systems and makes no statement as to their compatibility with our tachometers. If you have such a system, contact the ignition system manufacturer and ask if they have determined compatibility.



Tachometer Guide (Outboard)

All Teleflex 6K, 7K, or 8K rpm Tachometers and Tachometer/Hourmeters are suitable for use with Out board engines with alternators, except: Older Chrysler/Force Engines with 20-pole Prestolite alternators, which require a special tachometer, P/N 53743P, International High-profile style. These engine models include:

  • Chrysler Outboards: 55, 60 HP (1968-1983)
  • Force Outboards: (US Marine) 85, 125 HP (thru 1989); 90-120 HP prior to 1991 Revision 'H'; 150 HP prior to 1991 Revision 'B'
  • Force/US Marine L-Drives: 85 & 125 HP (1989); 90-120 HP (prior to 1991 Revision 'B')


Tachometers (Inboard & Stern Drive 4-Stroke Engines- Standard Ignition)

  1. Tachometer will not operate on a MerCruiser with Thunderbolt I (early 1970's era, but will operate on subsequent models) or an IndMar LT- 1 electronic ignition. Tachometer will operate with other OEM electronic engine ignition systems. Teleflex has not tested aftermarket systems and cannot guarantee their compatibility.
  2. Check all wire connections to see that they're tight and not corroded. NOTE: Some older style tachometers operate with only Ground and Sender connections. Teleflex tachs must have 12 VDC (from the ignition switch, "ON" when engine is running) to the "IGN" stud.
  3. When tachometer is first turned on, pointer must go to zero 50 RPM. If not, check connections (if OK, tachometer is probably faulty).
  4. Arrow on rotary selector switch must point directly at setting or the tachometer pointer may go to full scale when engine is started.
  5. Tachometer switch arrow should be pointed at 4C, 6C or 8C to correspond to the number of engine cylinders. Disregard other settings.
  6. The tachometer part number is stamped on the housing.
  7. Tachometer does have a "CAL" potentiometer feature to fine tune the tachometer a few hundred RPM or to sync two tachometers.
  8. Tachometer will also operate on outboard engines with an alternator having 4 through 12 magnetic poles.
  9. Dual stations: the send er will drive two tachometers. Connect "IGN" to "IGN", "GND" to "GND", etc. NOTE: mixing brands/types (such as 2-wire/3-wire, see paragraph 2 above) may cause problems.



Other Outboard Engine Applications

Rotary selector switch on rear of tachometer must be set to number of pulses from alternator per engine revolution. See Chart below (if your specific year/horsepower is not listed, see "All others" under your brand).




NOTE: Tachs will not work on engines with Magnapower I ignition. **88-115 HP "Special" models may require addition of an OMC Voltage Regulator to the engine, or a 2,000-ohm (or larger) resistor to the rear of the tach. ***Mariner 30 & 40 HP (2 cylinder) engines require a Module (Mercury P/N 17461A2) when using any of these tachs. **** Honda 40 & 50 HP models may require module (Honda P/N 06383-ZV5305 if tachometer is erratic between idle and 1800 rpm. Note: Engine designs are subject to change. Data above is based on the latest information available at the time of publication. Teleflex assumes no responsibility for its correctness or the misapplication of its products. Teleflex tachometers designated as O/B & 4-Stroke Gas Engines are compatible with all engine-manufacturer-designed electronic systems except Indmar LT-1 and (early 1970's era) MerCruiser Thunderbolt I, and have not been tested for suitability with aftermarket add-on electronic ignition systems. For help, contact Teleflex Electrical Technical Service at (941) 907-1000, Extension 8222.




Tachometer (Outboard Engines 4 Through 12 Pole Alternators)

  1. Outboard engine must have alternator (stator) with 4 to 12 magnetic poles. This is how the tachometer gets its signal. The tachometer will not operate on engines with magneto or lighting coil ignition systems.
  2. Check all wire connections to see that they're tight and not corroded. NOTE: Some older style tachometers operate with only Ground and Sender connections. Teleflex tachs must have 12 VDC (from the ignition switch, "ON" when engine is running) to the "IGN" stud.
  3. When tachometer is first turned on, pointer must go to zero 50 RPM. If not, check connections (if OK, tachometer is probably faulty).
  4. Voltages with engine running should be: IGN to GND Terminal: 12 VDC minimum. SEND to GND: 5 VAC minimum at idle. If you don't get the sender-to-ground voltages shown, voltage rectifier (converts AC to DC voltage) may be weakening. Have it checked.
  5. Sender wire must be connected (possibly through control) to either of two wires from alternator going to the rectifier (usually yellow or yellow/gray on U.S.-built engines).
  6. Arrow on rotary selector switch must be pointed directly at a setting or the tachometer pointer will go to full scale when engine is started.
  7. Evinrude/Johnson "Specials" (48, 88, 112 HP, etc.): If the pointer falls back to "Zero" when operating at about 4,000 rpm or higher, you may have to add a 2,000 ohm, 1/2 watt (or larger) resistor, connected from the "SEND" to "GND" terminal.
  8. Tachometer will not operate on older Force engines with 20-pole alternator. Consult engine dealer for number of poles in your engine.
  9. Dual stations: the send er will drive two "GND" to "GND", etc. NOTE: mixing brands/ types (such as 2-wire/3-wire, see paragraph 2 above) may cause problems.



Tachometer- Outboard Engines (Typical Outboard Rectifier Wiring)

Wire colors vary with engine manufacturers. The colors depicted are typical of Johnson/Evinrude and Mercury outboard engines. However, most engines use some form of yellow for the two wires from the stator to the rectifier.

For the outboard tachometer to be getting a proper signal on the "SEND" wire, the following AC voltages must be present at the yellow or yellow/ gray wire from Stator to Ground: Minimum 3.5 VAC (typically 6 volts or higher). The tachometer "SEND" wire can be connected to either the yellow or yellow/gray wire from stator.

NOTE: Wire Color Can Vary- on some Johnson/ Evinrude engines there may be a yellow/blue wire from the rectifier. This wire may some times be used for the tachometer sender connection with favorable results. In many domestic engine installations, the stator wires result in a gray wire routed to or near the throttle control where it can be used for the tachometer signal. Other engines have other color wires routed to or near the control: Yamaha- green, Nissan/Tohatsu/Suzuki- yellow, Honda- gray.

Always refer to the tachometer instruction sheet for wiring information.




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