Mercruiser Alternator wire overheating – engine stops - tip

Problem: Engine would stop suddenly at various RPM’s. Low voltage
indicated on dash voltmeter.

Vessel: 1997 Monterey 180, 190HP Mercruiser Vortec V6 I/O, Thunderbolt
ignition.

Electrical system was upgraded to a dual battery system with isolation.
OEM Mando alternator was replaced with Delco alternator since parts and
service were more available and economical.
Deep cycle batteries were used to allow extended use of lights,
entertainment, and electronic equipment.
When the batteries were discharged for about four hours the engine would
occasionally die, without apparent cause. Less than 12 volts was
indicated on the dash voltmeter.
Upon testing it was discovered that when the batteries were partially
discharged the orange wire from the alternator was too hot to touch.
Voltage measured at the batteries was below 12 volts and was often 11
volts. At about 10.6 volts the engine would die.
The alternator output wire was measured and calculated to be 10 gauge.
Charts indicate 10 ga. wire is rated at 22 amps continuous duty.
Alternator output is 55 amps or better.
Alternator output wire was supplemented with 4 ga. wire directly to
battery one. Voltage at battery and on dash increased to at least 13
volts. Orange wire runs cool. Engine ran for two hours continuously
after four hour battery discharge with no problems.

FYI


--
Dick Harper
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