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how can you identify if your ouboard has a charging unit,alternator

P

powers laker

Member
I have an 83 johnson 70 hp,and she is a hard starter,do these motors have some type of alternator,to help charge the battery while it is running,pretty sure mine doesnt,have to run a battery charger every couple of days down to the dock,if there is one can someone post a pic of what it might look light
 
The 1983 70hp Johnson indeed has a alternator charging system.

The large ring under the flywheel is a two fold component, the beginning of both the charging system and also the ignition system. On the starboard (right) side of your engine, the is a rectifier which converts the AC voltage of the alternator to DC voltage.

(Small Rectifier Description & Location)
(J. Reeves)


On most 2,3,4,6 cylinder engines, the small rectifier is located on the starboard (right) side of the engine just in front of the engines electrical wiring strip. There are a few older V4 engines that have the wiring strip on the rear portion of the engine and the rectifier would be located just under that terminal strip. The smaller horsepower engines usually have the rectifier located on the starboard side of the powerhead close to the carburetor area.


The rectifier appears to be a round object approximately one inch (1") in diameter and also about one inch (1") high. The base of it is sort of triangular in appearance and is attached to the engine with two (2) screws/bolts..... usually one screw/bolt is larger than the other. The rectifier, depending on which one your engine uses, will have either:


One Red wire, one Yellow wire, and one Yellow/Gray wire, or One Red wire, and two Yellow wires.

Note that either of the above rectifiers could have a fourth wire which would be Yellow/Blue
 
good tech. joe . if you have a garmin gps there a setting that will display voltage on screen, voltage should be higher when cruising then at stop with engine off
 
.Took the boat for a quick spin this afternoon to see the voltage,my humminbird also gives voltage.9.5,when motor is not running,9.5 when motor is running,yet fluctuated down to as low9.1,when motor was in gear and moving forward,I assume the volts should have gone up,,so from what I have read the rectifier might be bad?Any other way to troubleshoot this problem.
 
(Small Rectifier Test)
(J. Reeves)


Remove the rectifier wires from the terminal block. Using a ohm meter, connect the black lead of the ohm meter to the rectifier base (ground), then one by one, connect the red lead of the ohm meter to the yellow, yellow/gray, then the red wire (some rectifiers may also have a fourth yellow/blue wire. If so connect to that also). Now, reverse the ohm meter leads and check those same wires again. You should get a reading in one direction, and none at all in the other direction.


Now, connect the black lead of the ohm meter to the red wire. One by one, connect the red lead of the ohm meter to the yellow, yellow/gray, and if present, the yellow/blue wire. Then reverse the leads, checking the wires again. Once more, you should get a reading in one direction and none in the other.


Note that the reading obtained from the red rectifier wire will be lower then what is obtained from the other wires.


Any deviation from the "Reading", "No Reading" as above indicates a faulty rectifier. Note that a rectifier will not tolerate reverse polarity. Simply touching the battery with the cables in the reverse order or hooking up a battery charger backwards will blow the diodes in the rectifier assy immediately.
 
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