1974 115 Evinrude Charging

We have acquired a 1974 115 Evinrude which sat for at least 5 years. The good news is that it runs and idles, it even pumps running in the tank! We are going to put a new water pump on it in any case. The only problem so far is that it doesn't seem to charge. The rectifier tests ok, the ohms on the two yellow wires are within spec for a 6 amp system, and there is approx. 12 volts AC on the two yellow wires from the stator. I don't have a DC clamp on ammeter, but it will read approx. 1 to 3 amps on the AC side with an AC clamp on ammeter. DC voltage at the battery doesn't rise, however. Any ideas?

Re: 1974 115 Evinrude Charging

BTT

Re: 1974 115 Evinrude Charging

Hi,<br />If the diodes check out in the rectifier, the battery voltage on the yellow leads may only show battery voltage while running at lower rpms and if the battery is in a good state of charge. you may only notice a rise in voltage at higher rpms and with a partialy discharged battery.The system may be working properly. With the lower amp charging system the voltage increase will not be as noticeably high as you might see on a higher charging system. To accurately test the system you will have to discharge the battery, but still maintain enough voltage to start the motor, and run the motor on the water above 3000 rpm. With a multimeter connected to the battery terminals the voltage will show a reading greater than battery voltage. Hope this info helps.

Re: 1974 115 Evinrude Charging

Thanks o/b tech, that could be what it is, the battery was fully charged and I haven't run it up very high, since it was in a tank in neutral. I am used to the 35 amp systems on my 140 loopers, don't have any experience with the low amp unregulated system.

Re: 1974 115 Evinrude Charging

The charging system in that engine produces 300 volts A.C.to operate the CD ignition system. At idle the diode which produces half wave D.C.will control at close to battery voltage. If the engine runs, the charging system is working and so an AMP meter really isn't needed. At 3000 RPM the diode should regulate at no more than 16 volts or damage may occur.

Re: 1974 115 Evinrude Charging

You are thinking correctly-when you first start that engine, a voltmeter may show normal battery voltage-12.5 volts. As you run the engine for 15 minutes on plane (with some 3000-4000 rpms) the (unregulated) rectifier should start to charge the battery such that the batt voltage should start to increase from 12.5. After 20 minutes run on a fully charged battery, the voltage should get up to 16 or 16.5 volts and continue at that level till you turn the engine off. If you are not seeing anything but battery voltage, the system may not be recharging. Two possibilites. The rectifier may be bad. Typically when these are bad, the tach will usually also not function properly. If your tach functions normally, it may not be the rectifier. The stator has special/dedicated coils for recharging the battery. These coils are separate from the coils that fire the igntion system. The factory service manual has a section for checking the output of these charging coils.

Re: 1974 115 Evinrude Charging

Since the engine doesn't need battery current to run the ignition system as in the older single spark coil distributor systems the battery is only used to start the engine. Evinrude used an alternator with as little as 6 ampere current capability. If the diode fails in the short mode it may burn and destroy the stator. These engines at times will show signs of fire under the hood since they don't fuse the diode circuit. If you run at or near idle like a trolling motor for an extended period and restart the engine a number of times during the day the battery will tend to go flat, so it is more important in these engines to have a high quality battery and from time to time run at higher RPM for a while. In addition, a serviceable battery is advised since it may well need to be externally recharged from time to time which will boil off some water and a sealed battery can't be topped off with water. On a long day if the battery goes flat the cranking speed will fall and if the ignition supply voltage falls below 9.5 to 10.0 volts on starting the ignition module may well not trigger and the engine will get no spark. In these engines a solar cell battery float charger will be helpful to keep the battery topped off regardless of how the motor is used, however they tend to only produce a small current. It is also advisable to have a voltmeter on the dash to monitor the supply voltage especially during engine starting.