1988 4.3L shutdowns when the Alt. Belt slips

Sdraves102

Cadet
Joined
Aug 10, 2019
Messages
9
Alternator belt slip engine won’t stay started

Why doesn’t my 1988 4.3L mercuiser motor run on just the battery when my alt. belt started slipping. Is this normal for this engine? When I was tooling across the lake the belt started slipping and the engine kept turning off. I have a new bet in now but am hesitant to take it out until I know. By the way the battery is brand new and fully charged
 

Sdraves102

Cadet
Joined
Aug 10, 2019
Messages
9
Why is my 1988 4.3L Mercuiser Sputtering then shutting off when my alternator belt slips instead of running off the battery. Is this normal for that engine. Most Engines would keep running off the battery but this one seems to be running strictly off the alternator. I have a new alternator belt on but I’m hesitant to go out unless I know that this is normal. By the way The battery is brand new and fully charged.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Engine should run for a few hours on the battery alone. The belt slipping could also be a sign of another problem, like a shorted diode in the alternator, which could lead the the load on the battery being high enough to drop the voltage below the threshold of the ignition system, and stall the engine....

To test, disconnect ALL the wires from the alternator, insulate them with tape and start the engine and run it... If it runs without stalling, replace/repair the alternator...

Chris...
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,581
Only way I see this happening is if the ALT shorted out.
Put muffs on the drive and turn water on full. Start the motor and measure the voltage at the battery. Before motor is started, bat should measure 12.7V or close to. Once motor starts and is reved above 1500 rpms, there should be a steady 14+V from idle on up
 
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