Service Manual 5008330_55 HP MFE Electrical And Ignition [Charging System Tests]

IMPORTANT: An MFE 55 rope start model can be used to charge an accessory boat battery by installing a battery cable, P/N 584348, to the existing solenoid on the outboard..

To test the operation of the regulator in the EMM, you must be able to run the outboard continuously at approximately 5000 RPM, such as in a test tank
or on a marine dynamometer.

The test consists of monitoring the system’s response to a partially discharged battery. Use a variable load tester to discharge the battery.

IMPORTANT: The regulator requires voltage to operate. Before proceeding, make sure there is at least 7 V on the positive terminal of the starter solenoid.

Disconnect the battery cables at the battery.

Use an inductive amp meter or connect a 0 to 50 A ammeter in series between the red wire of engine wire harness (alternator output from EMM) and the positive (B+) battery cable terminal of starter solenoid.

Fluke† model 334 or 336, Snap-On† model MT110 or EETA501, and various other amp meters should be available through local tool suppliers.
Reconnect the battery cables.

Following the manufacturer’s directions, connect the variable load tester (carbon pile) across the battery terminals. Stevens model LB-85 and Snap-on model MT540D are examples of testers available.

Excessive battery discharge rates might overheat battery causing electrolyte gassing. This might create an explosive atmosphere. Always work
in a well ventilated area.

Variable Load Test Diagram

1. Red wire (alternator output from EMM)
2. Starter solenoid
3. Battery cable terminal (B+)
4. Variable load tester
5. Ammeter

Battery Charging Graph

Start and run the outboard at approximately 5000 RPM. Use the variable load tester to draw the battery down at a rate equivalent to the stator’s full output.

• The ammeter should indicate nearly full output, approximately 25 A @ 5000 RPM. Decrease the battery load toward 0 A.
• Ammeter should show a reduced output. As the current draw decreases, the battery voltage should stabilize at approximately 14.5 V.
• If results vary, check stator BEFORE replacing the EMM. See STATOR TESTS on p. 118.

Check battery ground cable for continuity.

With the key switch ON, check battery voltage at battery (12 V).

Then, use Electrical Test Probe Kit, P/N 342677, and a digital multimeter set to read 55 VDC to check voltage on white/red wires at J2 connector of EMM. Voltage at EMM connector should be 0.5 to 1 V less than battery.

1. J2 connector
2. Test probe

With outboard running at 1000 RPM, voltage on white/red wires should be 55 V. Voltage readings at a specific speed (RPM) should be steady.

If there is any other reading, perform STATOR TESTS on p. 118. Inspect the stator wiring and connections. Inspect the capacitor wiring, connections, and capacitor. Repair the wiring or replace a faulty capacitor, stator, or EMM.

Disconnect electrical connector from water valve solenoid. Use an ohmmeter to measure solenoid resistance.

1. Water valve electrical connector