Unattended electrical settings?


F

Fnsh1st

Member
What is best electrical switch setting for a boat in salt water 100% of the time.
I have read that the 12 volt side of the boat can add to galvanic corrosion issues.
My 37 PC has
2 - 12 volt main breakers, 2 - 120 volt main breakers

Currently when I leave the boat unattended.
Main electrical panel
120 volt side,
both mains on, and 3 breakers
house battery charging, refrigerator, freezer.
12 volt side.
one 12 volt main on with 1 12 v breaker on. It runs the refrigerator, which I figure will keep fridge running in the event of short 120v failure

There is also a single master 12 v battery switch aft with trash can, I leave this on


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Don't know what motor(s) you have, but need power to the motor(s) to keep the Mercathode (VP using similar) powered. The Mercathode is what protects the drives. The 12V house power is not needed for protection so you can leave it in either state, your choice.
 
AllDodge, Are you saying that I should be leaving the engine power switches, located on the bulkhead above the genset, on all the time? This keeps power to the mercathode? I'm pretty sure that I have a seperate breaker under the wet bar for that. I'll have to check. That being said, I assumed, ( I know, never assume), that the Mercathode was powered up regardless of battery switches, house or engine, similar to bilge pumps. I have Mercruiser 8.2 HO, engines 2015. I guess I better check, this week when I go down to the boat.
Great info from you, as always. That's why I really enjoy this forum.
 
Don't know where your engine battery switch is, but yes so long as the boat is in the water, don't turn the engine battery switch off. The Mercathode gets power from the power feeding the motor, normally from one side of the 50amp breaker (red/purple). Find the Mercathode and measure voltage on terminal b, should have battery voltage

Mercathhode.jpg
 
AllDodge said:
Don't know where your engine battery switch is, but yes so long as the boat is in the water, don't turn the engine battery switch off. The Mercathode gets power from the power feeding the motor, normally from one side of the 50amp breaker (red/purple). Find the Mercathode and measure voltage on terminal b, should have battery voltage

View attachment 9036
Click to expand...

Mmmm, in my previous boats the Merchathode is wired direct....something to check though.
 
I have done this test on my 08 PC power all the time.
Turned off all the battery switches and still has power.
When I take the boat out of the water I turn off the breaker marked Mercathode
 
All great information, glad to see others have gone down the same rabbit trail making sure they understand the systems.

I have not found the Mercathod unit yet in my 03 37PC, I thought it might be in the electrical cabinet like my Scarab, but after received my key to open it, it was not there, any ideas where to look?

I might as well ask about the factory installed galvanic isolator, I have not seen it, but know where it is.
Does anyone know how to confirm it is working properly. I assume it’s the factory installed unit.


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If the Mercathode came as part of the engine package from Mercruiser its on the motor, most on top. If it was added by the dealer or boat manufacture later, then it could be anywhere.

My 502 is inside the box on top the motor port side, my 454 is under the plastic cover next behind the carb on top the motor.

The 540 is on top the motor, starboard side behind the plenum,
 
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