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Author Topic:   Wiring Auxiliary Motor Alternator
irishcreamer posted 05-12-2009 01:47 AM ET (US)   Profile for irishcreamer   Send Email to irishcreamer  
Wow, great information here and great post by bluewaterpirate.Assuming the kicker has an alternator, how would that be wired in?

Many thanks!

jimh posted 05-15-2009 01:02 AM ET (US)     Profile for jimh  Send Email to jimh     
Assuming the kicker has an alternator, how would that be wired in?

In an outboard motor it is almost universal that the battery charging circuit is wired to the primary battery leads for the motor. This means there is no separation between the battery charging circuit and the battery. If you have a second motor of any kind, its alternator is wired to the battery that is connected to that motor. Unless the motor you have has some special battery charging circuit with extra outputs or isolated outputs, there is nothing to "wire in" with regard to the alternator of a second motor. It is wired to the battery.

Based on my own experience, I caution against configurations in which there are two motors running with their own alternators and the motors are wired in parallel to a common battery. This sort of arrangement puts the outputs of the two alternators in parallel, and this may cause problems. By problems, I mean cause one of the alternators to fail.

jimh posted 05-15-2009 01:12 AM ET (US)     Profile for jimh  Send Email to jimh     
[Separated from another discussion on a different topic.]
irishcreamer posted 05-15-2009 10:38 PM ET (US)     Profile for irishcreamer  Send Email to irishcreamer     
So,given a two battery system (primary engine, house) where the loads are isolated but the primary engine can charge both batteries, it is best to connect the kicker motor alternator to the house battery and avoid running both motors while the batteries are connected in parallel? This way minimizes the chances both alternators will be connected in parallel while running but still connects the kicker alternator to the battery system?

On the other hand, is the alternator on most kickers even strong enough to justify wiring it into the electrical system?

jimh posted 05-16-2009 09:16 AM ET (US)     Profile for jimh  Send Email to jimh     
If you have two motors, and they are both running, and their battery circuits are connected together, you may have problems with the alternators. Electrical circuits don't really care if they are connected together by a bus bar, a primary battery distribution switch, or by a combiner relay. When they're connected together they are connected together. That is how electricity works.

If you have two engines running, and they are both trying to charge a battery, and you connect them together, you will have wired their alternators together. I don't recommend this. If you do this, please let us know how it works out.

I recommend against this based on my own experience with outboard motors, batteries, and alternators. Some years ago I bought a boat that was wired so that its twin motors ran off a common battery. The seller said there was a little problem with the tachometer on one motor. The little problem turned out to be the alternator was burned out, a $300 repair. After the repair, the other motor's alternator burned out in a matter of a few hours. Another $300 repair. At that point I separated the wiring and never connected the motor alternator outputs together. The boat ran that way for years, and is still running that way with a new owner. No problems with the alternator on either motor.

This is why I don't recommend you wire the motors in parallel and charge a common battery. It is based entirely on my experience. As a fellow of good conscience, I don't go around telling people to do something when in my experience it causes problems. There may be others who have done this for years and had no problems, but I am not one of those people. I had problems with this, so I tell people that I do not recommend it be done. That is just my experience.

The two failures I experienced may have been due to poor design of the alternators, or perhaps totally random failures and not related at all to the wiring configuration. I did not want to repeat the experiment to see if it would blow up the alternator again, as the repair was rather expensive. However, I would be interested to see if your motors will blow up their alternator if wired in parallel. So if you try it, please let me know how it works.

SJUAE posted 05-16-2009 03:10 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     

I agree with Jim’s recommendation if you intend to run both engines simultaneously.

There seems an even split between those who have and have-not added additional battery cables and switch to support the kicker, when I enquired some months back.

I have just added a 9.9HP with 6amp charging on my 210 with dual batteries.

But I have not installed the extra wiring etc as I religiously only run engine at a time.

Once I get my dual binnacle sorted and if I find I am more tempted to run both, then I would follow Jim’s advice.


Ablewis posted 04-07-2010 07:20 PM ET (US)     Profile for Ablewis  Send Email to Ablewis     
Sorry for dredging up an old post but I have a related question and did a quick search first. Jim says there is nothing to wire in with the auxillery motor, but in my case there is. I have a 9.9-HP Honda kicker motor that has a pull start but does have an alternator that is not connected to the battery. I have never used that function and am wondering if anyone has a similar setup where they have used the alternator on the kicker to recharge the system? In my case, I would rarely be running both systems at the same time.
Ablewis posted 04-07-2010 07:53 PM ET (US)     Profile for Ablewis  Send Email to Ablewis     
I think I found my answer. I simply need to order a charging cable (part #31575-ZW9-000) which connects to the dc battery-charging receptacle on the tiller handle. Like Irish, I now need to figure out if this is worth it. A long day of trolling while running all the electronics has a tendancy to run down the house battery. In order to avoid the problem outlined in this post, wouldn't it be possible to simply wire a switch on the postive lead that could be turned on or off?

Anyone else with this [problem or circumstance] can find this cable part at: pdf

jimh posted 04-07-2010 09:01 PM ET (US)     Profile for jimh  Send Email to jimh     
I am afraid I am confused. Why would Honda make a motor with a battery charging circuit, but not provide a way to connect the battery charger output to the battery unless you buy an extra cable?
Ablewis posted 04-07-2010 09:29 PM ET (US)     Profile for Ablewis  Send Email to Ablewis     

I too am easily confused. I bought this kicker motor used. It may have originally come with this cable, but I never received it. The dealer that sold it to me said it would typically be used by a sailboat that could use this to recharge the battery on the boat.

SJUAE posted 04-07-2010 09:33 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     
I am also surprised that the cable is not included with the engine however the simple answer is yes if you want the extra precaution


number9 posted 04-08-2010 12:16 AM ET (US)     Profile for number9  Send Email to number9     
Took a look at my Honda Rigging Guide, the battery charge cord is included with the recoil start only motors when shipped new.
jimh posted 04-08-2010 09:00 AM ET (US)     Profile for jimh  Send Email to jimh     
Ah, the mystery solved! Now it makes more sense. Thank you.
RandyV posted 04-11-2010 06:01 PM ET (US)     Profile for RandyV  Send Email to RandyV     
Another question. Have you bothered to measure the output of the kicker motor at low RPM's? I have a Nissan 6hp kicker for trolling on my Montauk and added an alternator for keeping the battery charged but unless I use this motor at least half throttle, it won't generate enough voltage to charge a battery.

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