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Honda Outboard Battery Wiring

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bradandrose

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I'm going through the service manual for the twin BF150s that I'm getting ready to install and I've got a question on wiring my accessory battery charging circuit. This is a twin motor/twin battery setup. The starting battery and accessory battery are wired into a 1-2-BOTH selector switch and I normally start both motors off of the #1 battery. The #2 battery is for accessories only. The old Evinrude Fichts that I just pulled off the boat each had a built-in isolated accessory battery charging terminal so I had these terminals from both motors wired together and then into the positive terminal of the accessory battery. This way when either or both motors were running, the accessory battery was charging even though the selector switch is normally in the "1" position. This worked great. After searching through the Honda service manual, I'm not seeing a similar accessory battery charging circuit for the Hondas. How can I charge the accessory battery with the running motor(s) without having to move the selector switch to the "BOTH" position?


Also, It appears that the battery cables for these motors have three conductors; two heavy gauge (presumably to connect the starter relay and engine block to the + and - battery terminals) and one lighter gauge cable that the manual refers to as a "starter cable". This is connected to a plug in the main wiring harness. Where does the other end of this cable get connected??
 
I just saw this posting:

http://www.marineengine.com/boat-fo...-BF-150-Aux-Charge&highlight=battery+charging

The battery distributions center mentioned in this thread might be what I need, but it looks like the version for twin outboards requires three batteries; one for each motor plus a house battery. I've always started both of my motors off of a single battery, but I've done more reading that says that with Hondas this is a no-no. Anyone here run twin Hondas off a single cranking battery?
 
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Yep! I still stand by my recommendation.

That battery cluster minimizes any special cabling that you have to do.

Mike
 
I've attached a file from Bluesea's website that shows the exact setup that I'm looking to do. This is a two-battery system (one for starting, one house) where the starting battery feeds both motors and is charged by either or both motors when they're running. The house battery is charged by either or both motors through a ACR (automatic charging relay). This is basically the setup that I had with my Evinrudes except that the motors had built-in accessory battery charging circuits so I didn't need a ACR. Does anyone see any problem with starting and running both motors off of a single starting battery, particularly with Hondas? I'm seeing some stuff online that says that this is OK and some that says it's not. All I know is that I ran like this for 12 years/1200 hours with my Evinrudes and everything worked fine.View attachment Document1.pdf
 
"If the boat is equipped with two outboard motors, two batteries must be installed, one for each motor."

That is a quote from the first line of the Battery portion of Honda's Rigging Manual.

There has been previous discussion of this on the forum (somewhere).

Essentially, it you have two alternators trying to charge one battery, their regulators never really know if the battery is charged or not.

Of all of the BEP drawings, the one you posted is not in the rigging manual. This is the one in the rigging manual.

https://www.keoghsmarine.com.au/image/data/PDF/715-S Wiring Diagram 2 Eng 2 Bat.pdf

Mike
 
Ok, that's pretty definitive. I guess I'll have to change my setup.

How about my other question?:

"Also, It appears that the battery cables for these motors have three conductors; two heavy gauge (presumably to connect the starter relay and engine block to the + and - battery terminals) and one lighter gauge cable that the manual refers to as a "starter cable". This is connected to a plug in the main wiring harness. Where does the other end of this cable get connected??
 
If the other end of the smaller wire that you are asking about is at the battery end of the cable, it goes to the positive side of the battery. When the engine is new, it shares a cable lug with the large positive battery cable.

The reason for the separate smaller cable is to minimize any voltage drop to the ECM during start up. The heavy draw from the starter goes through the larger cable.

The plug end at the engine side ultimately goes to the fuse panel.

Mike
 
We have just purchased a used 4 stroke 75hp Honda outboard, trying to wore the battery in and cant find where the negative cables connects to the engine. Can find the positive but can't find the negative. Any help would be appreciated.

Thanks April
 
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