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Old 06-23-2017, 02:32 AM   #11
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mercruiser 7.4 wiring diagram

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Google 7.4 wiring diagram
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Old 06-25-2017, 12:18 AM   #12
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I'm trying to figure out the 3 way battery switch. I moored for 24 hours with the switch set to one(1) and killed the battery with the fridge, lights and stereo. With the switch set to ALL (3 batteries) the V8 started like a charm. I then switched back to one(1) with the understanding that that battery would be charged on the return trip. Upon docking in my boat house and plugging into shore power I returned the switch to ALL once more expecting the built in charging system to do its thing. Any guidance/corrections/ or gentle ridicule will be appreciated.

Also, my tach, speedometer and trim gauge are kaput. Could this be related?
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Old 06-25-2017, 03:28 AM   #13
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Not clear what the issues is, are you saying battery one was not charged? How long was the trip back to home port? The engine alternator puts out around 60 amps if the battery is a 700 amp hour battery it will take several hours to charge.

No the gauge issues are not related to the battery nor each other.

Check the tach sense wire (gray) for voltage.

Check the speedo pitito hose to ensure its connected on the drive.

Check the trim sendor wires to see if they are broken, puck on the side of gimbal ring.
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Old 06-27-2017, 12:19 PM   #14
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A 3-way Battery switch (I assume) would be 1 ; 2 ; BOTH ; OFF. This would only allow for 2 positive terminals.

With 3 batteries, I assume that you have a starting battery bank and a house bank. With three batteries, I would guess that two of them are wired in parallel. The two batteries paired in parallel would the house bank and the single battery would be the starting batter.

Frequently the starting battery is wired to switch position 1 and the house is on switch position 2. It would be helpful to verify as this is A LOT of speculation on my part based on my boats have been wired.

You should start and run on the starting battery, then switch to the house bank whenever the boat is stopped. Battery charger should be a three bank charger and wired directly to each battery.

Note that the alternator will only charge whichever battery the battery switch is switched too. It is my understanding you should not run with the switch set to ALL.
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Old 07-05-2017, 09:57 PM   #15
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Fuel tank is 102 gal, water is 30 gal and waste 16 gal!
There should be a GFI receptacle, check at all 110 volt outlets for a GFI and reset if tripped!
The holding tank you will have look at to tell if it needs to be pumped out!
Hope this helps!
I have the original owners manual for the 2400 and 2700 SCR's if you PM me with your email I will try to send the wiring diagrams!
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I reset the one GFI and two of three outlets now have power! Therefore my wife's hairdryer will work when we're docked = thank you!
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Old 07-05-2017, 10:06 PM   #16
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There's a starting battery and two deep cycle batteries. As I understand it the switch should be on ALL when plugged into shore power as this allows ALL to charge. I should set the switch to ONE when starting and leave it there while running as it will recharge. Upon mooring/anchoring without shore power I should set the switch to TWO which draws upon the TWO deep cycle batteries. (and set the 'fridge to one to conserve power) I'll let you(se) know if I screw up though I travel with a charged battery pack so I'm not too worried.
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Old 07-06-2017, 12:21 AM   #17
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Quote:
Originally Posted by Jeff Kuryk View Post
T As I understand it the switch should be on ALL when plugged into shore power as this allows ALL to charge.
Battery switch determines which battery is being drawn from. It will also dictate which battery is being charged by the alternator (when the engine is running).

When connected to shore power, the battery charger breaker would need to be turned on. The battery charger should be wired directly to the batteries and not through the battery isolation switch.

If you have 3 batteries, you should have a 3 bank battery charger. It should be a smart charger and have the ability to sense and charge each battery independently.

I try to make it a rule: Start and Run on the starting battery, and Sit on the house battery.

Even if you're on shorepower, you would want to be drawing off the house battery if there is a temporary power outage locally or on the dock.
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