1996 90 hp Johnson Alternator question

What is the alternator output for a 1996 90 hp JOhnson Outboard motor? I am trying to hook up an auxiliary battery charger for my boat and the MinnKota specs call for a 35 amp minimum alternator output for the charger to work properly. That sounds really high. Any ideas?

TnTom said:

What is the alternator output for a 1996 90 hp JOhnson Outboard motor? I am trying to hook up an auxiliary battery charger for my boat and the MinnKota specs call for a 35 amp minimum alternator output for the charger to work properly. That sounds really high. Any ideas?

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Depending on the model of your outboard, you do not have an "alternator". The batteries in your boat are charge by the Stator. I'm guessing your stator is rated at 9 amps, however it is possible to get a 35 amp stator, again depending on the model of you engine.

How that helps.

"Depending on the model of your outboard, you do not have an "alternator". The batteries in your boat are charge by the Stator. I'm guessing your stator is rated at 9 amps, however it is possible to get a 35 amp stator, again depending on the model of you engine."

My plate on my engine says it is a Johnson Ocean Runner V4 90hp. Model No. J90SLEDR Serial No. G 04065632 CE 95 Power 67 Mass 145. Is it possible to upgrade the stator to 35 amp? I assume that is what MinnKota is talking about when it says an alternator with 35 amp output. What kind of costs should I expect from the mechanic to install the upgrade?

it sounds like you are trying to run a trolling motor that takes 35 amps minimum...that has nothing to do with your charging output...the 35 amps will come from your battery.....you are not going to be running your outboard engine and the trolling motor at the same time...what they are saying is for example if you run your trolling motor for one hour and draw 35 amps then you would need 35 amps charging rate for one hour on the outboard to get the battery back even...
the normal setup would be to have an ignition battery and a separate deep cycle battery for your trolling motor...a good deep cycle battery will run the trolling motor for hours and most people charge them with an external charger that night or whatever...then you are ready to go the next day..the charging system on the outboard will charge the ignition battery when running...... so you dont have to recharge it at night..a good charge on the deep cycle will run a trolling motor as much as an average fisherman will use in a day....
you can get fancy with splitters and/or switches if you wish and charge your trolling motor battery while running the outboard but i prefer to keep it simple...one reason for this i want to make damn sure i have a hot ignition battery at all times...and not run it down with a trolling motor...
forget the upgrade if you go this route...you dont need it....

turk said:

Depending on the model of your outboard, you do not have an "alternator". The batteries in your boat are charge by the Stator. I'm guessing your stator is rated at 9 amps, however it is possible to get a 35 amp stator, again depending on the model of you engine.

How that helps.

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Of course he has an alternator. What the heck are u smoking? The stator IS an alternator.....

Magneto?

Smoking that ol' magneto again???? LOL....

I got this form the 'net...

"A magneto has a permanent magnet moving past a single coil of wire-- The changing magnetic field induces a voltage in the coil.

The voltage is going to be a big spike, not too useful for anything other than firing a spark plug. Yout basic lawnmower probably has a magneto. So do the older airplane engines. The reason they both use magnetos is that they're dead-simple-- nothing much to go wrong. You can shoot up an airplane and knock out all its electrical power and its engines will keep on going (pre-jet planes only).

An alternator has several coils around a magnet, usually an electromagnet although it could be a permanent magnet also. Most cars have alternators with an electromagnet in the center. Just like in the magneto, the magnet spins around and induces voltage in the coils. There are usually three or more coils, so the voltages get sent out as three separate phases to a rectifier and that makes a kinda wobbling DC that is just fine for charging the car battery."


He has an alternator by virtue of the stator and flywheel magnets.

TnTom said:

What is the alternator output for a 1996 90 hp JOhnson Outboard motor? I am trying to hook up an auxiliary battery charger for my boat and the MinnKota specs call for a 35 amp minimum alternator output for the charger to work properly. That sounds really high. Any ideas?

Click to expand...

I've been following this thread, lurking in the darkness, trying to gain some sort of insight... but apparently I have not the mentality needed to grasp the full meaning of the question.

The 90hp model mentioned does indeed have a alternator, built into the stator via a series of coils that supplies AC voltage to a rectifier which is designed to convert the AC to DC voltage needed to charge the attached 12v DC battery. Seems to me that is all that's needed.

The posed question appears to insinuate that one is attempting to wire in a battery charger that is powered by the engines alternator in order to charge that battery?

To my knowledge, all battery chargers are powered by 110/120 AC voltage, most of which are designed to charge any 6v or 12v battery.

What am I missing here?

i dont think you are missing anything joe...he could indeed hook up the trolling motor to his ignition battery and pull 35 amps from the battery to run it...i was just trying to tell him that i dont think thats wise..maybe i have a hangup about running the ignition battery down...but i have a couple friends that have spent a night each in the louisiana swamps listening to alligators growl...instant PTSD for both of them...
maybe i read something wrong in the original question...but as far as i am concerned he has 3 choices...#!...hook the trolling motor up to his ignition battery with the existing charging rate and use it...#2..buy the stator and regulator and spend 5-700 bucks and install splitter,switches etc..he can either run one or two batteries on this setup...i would prefer two...#3...run a separate battery for the trolling motor and charge it from a 120/12v charger when the boat is docked or at home ...