Re: Tach problems
Howdy,<br /><br />I'm having tach problems with my 1983 Mercury 50 HP. I was on the Teleflex webpage today and found something that might help you. Check out the part about the "Special" engines. It's number 7 below.<br /><br />Good luck,<br /><br />Terry G.<br /><br />6980 Professional Parkway East<br />Sarasota, FL 34240 USA<br />Phone: (941) 907-1000<br />Fax: (941) 907-1020<br />COPYRIGHT 1998 TELEFLEX, INC. (USA)<br />OUTBOARD ENGINE TACHOMETERS<br />4 THROUGH 12 POLE ALTERNATORS<br />1. Outboard engine must have alternator (stator) with 4 through 12 magnetic poles. This is where the<br />tachometer gets its signal. Tachometer will not operate on engines with magneto or lighting coil ignition<br />system. Tachometer will not operate on older Force engines with 20 pole alternator. Consult Application<br />Guide or engine dealer for the proper number of poles on your model and year Force engine.<br />2. Check all wire connections to see that they're tight and not corroded. Note - Some older style tachometers<br />operated with only Ground and Sender connections. Teleflex tachometers must have a 12 vdc (from the<br />ignition switch, On when the engine is running) to the IGN stud.<br />3. Voltages:<br />IGN to GND Terminal - 12 volts DC Minimum.<br />SEND to GND - 3.5 volts AC minimum at idle - 5-7 volts AC at approx. 2000 RPM.<br />If you are not getting sender to ground voltages, voltage rectifier may be starting to weaken (converts<br />AC to DC voltage). Have it checked.<br />4. When ignition is first turned on, tachometer pointer must go to Zero +/- 50 RPM. If not, check<br />connections or tachometer is defective.<br />5. Sender wire must be connected (possibly through control) to either of two wires from alternator going to<br />the rectifier (usually yellow or yellow/gray on U.S. built engines).<br />6. Arrow on rotary selector switch must be pointed directly at a setting or the tachometer pointer will go to<br />full scale when engine is started.<br />7. Evinrude/Johnson Specials (48/50, 88/90, 112/115 hp etc.): If the pointer falls back to Zero when<br />operating at about 4000 rpm or higher, you may have to add a 2000 ohm, 1/2 watt (or larger) resistor,<br />connected from the Send to Grd terminal.<br />8. Dual stations - mixing brands/types (such as 2-wire/3-wire, see paragraph 2 above) may cause problems.<br />9. Cal adjust is used only when RPM reading has drifted consistently over time. Cal adjustment will not cure<br />erratic readings.<br />OBTACH_TS.PM6 10/21/97
