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Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

Outboard Alternator output

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Scooter
Navigator

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USA
228 Posts

Initially Posted - 08/29/2005 : 14:36:25

I am told that a car alternator is a 100 amp "charger". Does anybody know what a Johnson '89 (guess at year) 9.9 hp has for an alternator ouput?

Scooter
C25 '89 SR/WK #5878 "Square Knot"
Vandemere NC.

Edited by - on

JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 08/29/2005 : 15:20:54

the Honda 8 hp is 5 amps but only at near full throttle (5000 RPM). At lower settings you are probably getting about 2. For that low power, combined with the small amount of time I spend motoring, I've never bothered to hook it up. My 3 amp Guest shore power charger and 3 amp solar panels are all that is needed.

One thing, I did measure the DC voltage at 25 volts coming off the motor. Similar to my solar panels which are also about 22 volts in full sun. But these currents are low so they do not bring the overall system voltage up to a level that can cook your batteries, unless left on for a very long period of time. Thats what the voltage regulators are for.

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Steve Milby
Past Commodore

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USA
5937 Posts

Response Posted - 08/29/2005 : 17:52:57

I don't know what the output is, but it isn't much. I've run my battery down by starting my Merc 7.5 with the electric starter and not running it long enough to recharge it.

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tinob
Master Marine Consultant

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USA
1883 Posts

Response Posted - 08/29/2005 : 19:51:47

Scooter,

The manual that came with my 9.9h.p. Johnson sailmaster circa'93 claims 5amp output. I don't know if this is so. I've never checked it. I've had no reason to question it. What I do know is that since new it has provided all the juice that my two deep cycle 24's need over the season in the n'east. I generally sail daily May to November weather permitting and do about 30/45 minutes each day. Just getting out to the bay and then back. If the wind is agreeable I'll sail to/from the slip.
I sometimes put a charger to them dockside, not because of need but for lack of anything to do that day.

Off season they are stored in the barn and charged to capacity and maintained that way over the winter.

So far no problems. Since '93 that is.

Val on Calista # 3936

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aeckhart
Master Marine Consultant

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USA
1709 Posts

Response Posted - 08/30/2005 : 10:31:51

My 88 Evinrude 9.9 Yachtwin manual states 4 amps.

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seastream
Navigator

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USA
242 Posts

Response Posted - 08/30/2005 : 22:00:04

What Aeckhart said. I've got the same motor, but an '87. We motor an hour plus to get offshore; although that's 2-3 hours chargetime roundtrip, it's not enough when overnighting a weekend or so. I have two 75 AH batteries. I bought the 1.2 AH solar panel from WM for $150. Well worth it. Bought the $30 regulator as well, haven't used it yet.

Bob

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Dave Bristle
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Djibouti
10005 Posts

Response Posted - 08/30/2005 : 23:25:47

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by JimB517
 the Honda 8 hp is 5 amps but only at near full throttle (5000 RPM). At lower settings you are probably getting about 2.<hr height="1" noshade id="quote"></blockquote id="quote">
That's the "classic" 8. The current model pushes out 12 amps at full throttle, and I think 6 at idle. That's very high for a an 8-10 hp outboard--most are 6 or less wide open. I've been pleasantly surprised at how quickly it brings a dead battery far enough up to power the electric starter, which is the biggest challenge for most of our batteries. (I also like that if I let the battery die, I can pull-start the engine!)

Edited by - Dave Bristle on 08/30/2005 23:33:03

Scooter
Navigator

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USA
228 Posts

Response Posted - 08/31/2005 : 08:47:49

Guess I'm just going to have to measure the voltage coming off the OB alternator. Don't like the 25V measured by Jim. If I go with Gells that would cook them.

For those interested I called "Discover Solar" http://www.solarelectricinc.com/ and asked about DC regulators. After a few questions they gave me the name of the regulator mfg and I called them. They said DO NOT put a regulator in line with the motor's alternator. They said they "used to" make a serial regulator but not many people are making serial (can put in series) alternators anymore. They only make "shunt" regulators now. If you put a shunt regulator in series with the motor's alternator you will ruin the "new" regulator. They said the OB alternator should already be regulated by itself. Most A/C chargers are also regulated.

I will have to do some testing myself instead of "guessing". This group is the first place I could get a decent answer about OB outputs. None of the places I called that service OBs could answer these questions.

Since we are planning longer voyages this solar thing is getting me interested. Have to do more digging but seems like less hassle, safer for the battery, and environmental in the long run.

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Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 08/31/2005 : 10:51:17

If anyone knows what the Tohatsu kicks out, I'd like to know. Not being an electrician, I can't tell if the diagram located here http://www.tohatsu.com/tech_info/own_man_pdfs/8_98.pdf near the back of the book actually indicates it or not. I have the two stroke 8 hp electric start with alternator

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JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 08/31/2005 : 11:10:31

Scooter, I have 3 11-watt flexible solar panels from Discover Solar (you should get one 33 watt panel). These put out 2.5 amps. I also have the voltage regulator. I have an oil lamp, and several candles. I have autopilot, stereo, VHF, fishfinder, and a Davis mini-mega anchor light (I hoist it up the backstay with the main halyard). I have replaced my interior lights with halogens. I had my laptop computer on the voyage. I have an inverter and charged my laptop plus my cell phone.

My solar set up + 2 Group 24 Gell batteries powered my boat just fine on my 3 week cruise - even with many foggy, cloudy days.

The advantage of the flexible panels - you can throw them anywhere (deck, boom), you can tie them down with a little light line, underway or at anchor, you can walk on them. The guy at Discover Solar said you could shoot a hole in them and they would still make power. They cost $95 each at Discover Solar (over 150 at West Marine).

As I said, my OB is always getting wet and there is just no good way to run the electrical power into the boat, through the fuel locker! and to the batteries. So I have it all disconnected, cut off and inside the motor the wires are covered with liquid electrical tape. It doesn't put out much power anyways and I sail alot.

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Tom Potter
Master Marine Consultant

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USA
1913 Posts

Response Posted - 08/31/2005 : 17:19:46

Duane,
I have a 1995 Tohatsu 8 hp 2 cycle. According to Tohatsu it puts out 5.8 kw at 5000 rpm.

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frog0911
Master Marine Consultant

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USA
1349 Posts

Response Posted - 08/31/2005 : 19:53:31

Duane, my 04, 9.8 Tohatsu, 4 stroke puts out 7.2kw at 5000 rpms, which makes the amp ouput 6 amps at 5000 rpm.

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atgep
Master Marine Consultant

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1009 Posts

Response Posted - 08/31/2005 : 20:40:49

The KW rating has nothing to do with alternator output. It is a hp conversion to k-watts of power rating for the powerhead. I suspect it is a metric thing.

Tom.

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JoergK
Navigator

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USA
140 Posts

Response Posted - 09/02/2005 : 13:32:28

Tom is right, Frog.
Otherwise, you'd have 1200 Volts (7200 watts ./. 6 amps)!!!

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frog0911
Master Marine Consultant

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USA
1349 Posts

Response Posted - 09/02/2005 : 21:16:52

Well screw that up, but found my spec. sheet and it says 12V, 80W, 6.7A. So I was close , but no cigar.

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seastream
Navigator

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USA
242 Posts

Response Posted - 09/03/2005 : 22:58:59

One of the reasons you shouldn't put a solar panel regulator in series on the leads between the engine and battery is because the high starting current requirements of the motor could likely fry the regulator. Best to make sure said regulator is between the panel and battery only.

BTW, one horsepower = 746 watts. Don't know how that was derived but I don't think anybody made a horse light up 746 one watt lightbulbs or anything like that.

Bob

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