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Mercruiser power problems

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chip sullivan

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"I have twin Mercruiser 260 st

"I have twin Mercruiser 260 sterndrives. There is a power problem with the port engine. it will run fine and then, bam, just shut down with no power at all to the gauges, starter etc. If I trip the "emergency" button to combine the batteries from the starbord engine, sometimes that will cause the power to come back to the engine and it will start up and run for a while before the whole process is repeated. My yard guy thinks it may be a bad battery cell and is recommending new batteries but this does not sound right to me. Thoughts?"
 
Loose engine barrell plug will

Loose engine barrell plug will cause it to quit under vibration. Have the batteries both tested for specific gravity. All cells should be nearly the same. If 3 yrs. old they have done their duty.
 
"chip;
Sounds like an outage

"chip;
Sounds like an outage in your main power feed thru the 50 amp breaker on the engine.
The best way to find what it is would be to start circuit tracing next time it happens, and find out where the power stops.

It could well be corrosion at the 10 pin plug where the boat harness connects to the engine, as Guy has suggested. This should likely be your first check. The circuit in question is a heavyish red wire. About a #8 gauge.

You may also have an intermittent 50 amp breaker. In many ways that would be the best scenario as they are easy to replace. It might be a bad key switch for that engine, since the key switch controls all gauge power also. Does switching the key on and off a few times do any good?

If you need I can send you a discussion about how the main power feeds. This will help you trace it. Let me know.

Rod"
 
"chip;
Sounds like an outage

"chip;
Sounds like an outage in your main power feed thru the 50 amp breaker on the engine.
The best way to find what it is would be to start circuit tracing next time it happens, and find out where the power stops.

It could well be corrosion at the 10 pin plug where the boat harness connects to the engine, as Guy has suggested. This should likely be your first check. The circuit in question is a heavyish red wire. About a #8 gauge.

You may also have an intermittent 50 amp breaker. In many ways that would be the best scenario as they are easy to replace. It might be a bad key switch for that engine, since the key switch controls all gauge power also. Does switching the key on and off a few times do any good?

If you need I can send you a discussion about how the main power feeds. This will help you trace it. Let me know.

Rod"
 
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