# Running an outboard motor that has a generator without a battery is bad?



## tenuki (Feb 11, 2007)

i'm kinda embarrassed to admit this, cause I have a degree in Electrical Engineering, I just wasn't thinking...

I ran my outboard all summer without connecting it to a battery. It's a Yamaha 8hp electric start and alternator, with pull start too, so I've just been pull starting it and had the leads that would normally connect to a battery just covered and isolated. duh.

When I pulled it this fall for maintenance, I started thinking.. you know, it probably is very damaging for that alternator to run without a load of any kind. I'll know if I did any damage when I do the maintenance and then re-install it with a battery but it sucks I didn't think of that earlier.

What is everyone's opinion on this, I was pulling it out when it dawned on me, don't know if it's common knowledge or not.


----------



## artbyjody (Jan 4, 2008)

You are ok....


The starting energy is mechanical to electrical and honestly - you would be better off having a battery system for it to tie to.. but in a generic sscenario you have a lawn mower.. you yank it starts...


If you want the ability to be more self sufficient get the interface kit and install batteries and you can begin to9 enjoy extended cruising...

But as it is - you are ok..


----------



## tenuki (Feb 11, 2007)

That's the thing, it already has an alternator built into the motor. Running it open circuit without load means the voltage can float and get out of hand, burning it out. I hope that hasn't happened yet, I'll let you know what the yamaha dealer says. 2006 yamaha T8h


----------



## artbyjody (Jan 4, 2008)

But its not hooked to anything.. so what is the issue


----------



## tenuki (Feb 11, 2007)

Here is a discussion of the issue. and again here. 

Basically the alternator is running when the motor runs, so either the diodes or the stators are in jeapordy because it can develop high voltage spikes in open circuit mode. If it has a battery the battery acts to regulate the voltage by providing a load, so no spikes or floating.

I was planning on just adding a battery anyway, so just crossing my fingers that there hasn't been damage.


----------



## artbyjody (Jan 4, 2008)

if you haven't had problem...you are probably ok... it is shunting the energy one way or the other but if an alternator is not connected to something - nothing is happening... <sorry for="" the="" sarcasm="" -="" but="" they="" teach="" this="" stuff="" to="" get="" a="" degree="" yes?=""></sorry>


----------



## tenuki (Feb 11, 2007)

artbyjody said:


> you are do have Electrical Degree right? <sorry for the sarcasm - but they teach this stuff to get a degree yes?>


Yes, which is why I understand that it may be a problem. What about you?


----------



## haffiman37 (Jun 4, 2004)

There should be no problem.
The generator system on outboards consists of 1 or more seperate charge coils under the flywhel. Total output at max rpm is probably no more than 8amp, and drastically reduced at lower rpm's. Most outboards with pull and el starts may run not connected to any battery, BUT b sure the battery cables have isolated ends. Only if the + and - gets together the diode and coil will be dammaged. Open loads should be no problem.


----------



## artbyjody (Jan 4, 2008)

was idiot and post reflects that - my apologies


----------



## tenuki (Feb 11, 2007)

artbyjody said:


> I don't own a degree just worked on nuclear submarines with them thinking I had some semblance of understanding I understood electronics .... but your degree trumps my experience - kudos...see you next year at the north pole...


hmnn, somebody got up on the wrong side of bed today.


----------



## tenuki (Feb 11, 2007)

If you need some higher authority on wether this can be a problem or not read this.


----------



## duffer1960 (Aug 11, 2000)

My first sailboat came with a Johnson 9.9 with an alternator and electric start, but with none of it hooked up. The original owner just pulled and started and ran. After I had it a couple of years and added some electronics and a stereo I thought it may be a good idea to hook up to the alternator to keep the battery juiced up, and it would be nioce not to pull the rope all of the time. Everything worked with no problem and the alternator keeps the battery charged. You shouldn't have any problems either.


----------



## chucklesR (Sep 17, 2007)

Simple check, take a multimeter to the blocking diodes and check. Takes 5 minutes, no need to wait until summer. If blown, takes 5 more minutes to replace.
No degree, but after 2 years of school I did fix Radio and such on the same submarines that Jody watched dials on


----------



## Gryzio (Dec 13, 2007)

*I not want to mislead you, but .....*

Back when I worked for a boat dealer I never seen many problems with Alternators (Stators) on outboards, and the ones I did see where not because of Batteries. 

Many small outboards come without a Starter or battery. They run off the Stator (Magnetics are on the Flywheel similar to Lawnmower engines).

Many times I installed starters on these little engines and of course a battery. I never changed the Stator for more output. Just mounted the Starter, Solenoid etc. (Most already have the screw holes). 

It been many years I worked on boats in a Professional Environment (Still do some work for Friends).

I would play it safe and ask the Dealer of that Engine for an opinion. Normally I can call and ask for the repair shop and ask a mechanic his/her opinion. I will almost bet $5 it not hurt. 

I add this; Remember it does have some load as the Stator is what makes the Voltage for the Coils to spark the Plugs.


----------



## tenuki (Feb 11, 2007)

Gryzio said:


> I would play it safe and ask the Dealer of that Engine for an opinion. Normally I can call and ask for the repair shop and ask a mechanic his/her opinion. I will almost bet $5 it not hurt.
> 
> I add this; Remember it does have some load as the Stator is what makes the Voltage for the Coils to spark the Plugs.


Cool, thanks for the replies everyone, nice to know it isn't a common problem.

Yup, I'm planning on talking to the shop when I take it in for it's 10 hr and asking to look at the shop manual too, the owners manual doesn't have a schematic. Then I'll know for sure for my motor.

btw, I remember reading that outboards use a different stator for ignition/running and charging, although it is usually located in the same place. So the alternator doesn't have load if that is true.


----------



## sailaway21 (Sep 4, 2006)

Is it actually an alternator or is it a generator? You'll do no harm to an unloaded generator but could possibly blow a rectifier on an alternator.


----------



## tenuki (Feb 11, 2007)

sailaway - alternator.


----------



## sailaway21 (Sep 4, 2006)

Well, I'm no expert on this, I don't even play one on TV and I can't even afford to stay at a Holiday Inn Express, but I'd guess that the question would be whether the alternator is regulated or not. Given the low output, I'd guess that it's unregulated which would allow it to possibly overcharge (?) but sustain no damage from running with no load. Probably just enough knowledge to be dangerous or a swag (scientific wild ass guess). You pick.


----------



## billyruffn (Sep 21, 2004)

Tenuki,
I think you're right. I read in a number of places that you never disconnect an engine w/ an alternator from the battery when the engine is running. You've probably blown the diodes in the alternator -- but then I don't have a EE degree, I just read a lot and try to do what smart people tell me to do.


----------



## tenuki (Feb 11, 2007)

The only thing I've actually used my EE degree for was making my own one of a kind guitar effects for my punk and art noise bands.  But I still remember stuff occasionally, which of course is worse than knowing a little (ie knowing a lot but remembering it poorly).


----------



## haffiman37 (Jun 4, 2004)

The system is as simple as can be on those small engines:
1 (normally) coil under the flywheel.
1 simple diode rectifier on the ouside somwhere.
The output is at the best [email protected] Even at full throtle You will not be able to 'boil' a simple lead acid battery.


----------



## artbyjody (Jan 4, 2008)

I did some research - and again apologies. You are rightfully to be concerned but for the reasons that you thought. 

An alternator when not properly shunted (mind you that means excess energy over live load - is being discharged...) can cause issues. My erroneous (and making an ass of myself ) statement - actually there are two things can happen in your present set-up.

Alternators produce "energy" for lack of anything else... unless the alternator is disconnected on the belt side or you have proper shunting in place... yes you will kill the alternator and perhaps anything within earshot of it..(depending on whether or not you have loose wires BUT)...

The issue really is are you causing in damage with you setup - and that would be a resounding yes unless the alternators output is being shunted. If not you probably will encounter when you add a battery and the supporting electronics they never get charged because the alternator spins and yet produces no voltage. While alternators in general are pretty forgiving - less your time of operating with it not having any kind of load - it is possible the damage you may have incurred is the alternator fired itself.

The only way to know is to measure the output of the alternator... and if you have been so lucky investigate what it would take to shunt the energy..until you install a proper battery / electrical system. 

In summary you are rightfully concerned. If the alternator never had a load or was improperly configured without a load... you do run a risk of severe galvanization (if the alternator is not properly grounded and working then is the grounding system?) but more importantly where is the output directed to? 

So you may desire to investigate what would allow your vessel to be more safe and productive with actually using the resources your motor is allowing you to embrace...but is is plausible - with no real load on the alternator that it just spins up and burns itself out...depending on the type of alternator or how is it is hooked up... but it would spin.. However personally - considering if it is a marine alternator, your are better of than say this being a situation of a automotive alternator...


However, this is where you are safe... your outboard was not explicitly designed to have such, hence why I had such an ignorant comment... If not designed but you add to it - it is more than likely it is not generating anything.. most of the later day technologies - are much more intelligent than say 30 yrs ago...so it is more likely because you never hooked up a battery you never lost anything to begin with... my outboard has the same deal - I can add it - but unless I add everything else kinda pointless...

You are probably ok - but if you have it invest in the rest of the mechanism for boating..its paid for electricity... can power a Xbox your nav lights and heck an electric coffee maker if you do it right...


----------



## haffiman37 (Jun 4, 2004)

ARTBYJODY:
'Interesting' but not quite relevant for the type of charge system we are dealing with, which is in general standard for outboards.

The main difference is: There is no electric field circuit, either by separate 'Field' cable or from regulator.
With 'OPEN LOAD' there is simply NO current/amps flowing anywhere in the system.
The charge/light coil normally has 2 or 3 wire coming out. Any current created is from induction caused by the flywheel magnets passing the coil, and the magnetic field is close to constant. (In fact it is reduced slightly by rpm, but that is another story.) To be able to get a current in the cables they must 'get together' in one way or the other. You may hook up a nav light and use the AC current, or hook up a set of diodes to make a DC current. However still if You leave the B+ DC with open load, still no current will flow!! Nothing gets 'burned' nothing gets damaged.
A belt driven alternator normally operates a bit different. The field current is controlled by the regulator and will be encreased trying to bring up the B+ to preset charge voltage. If an 'open load' there will be no charge voltage/current, the field will try to give more, finally it BURNS! Similar thing might happen if You have a low rated alternator trying to charge a too huge battery pack with low charge level. It will take too long time for the batteries to get charged, the field BURNS! Your alternator capacity in such a set up should be minimum the 20% of the banks amp/hour capacity, or 20Amp alternator on a 100Amp/hour battery.
But in the outboard case:Run with 'open load' as long as You like, the system is not active!!!!


----------



## thekeip (Aug 8, 2007)

Say what??

howard keiper


----------



## tenuki (Feb 11, 2007)

did anyone even read the links I provided?


----------



## tenuki (Feb 11, 2007)

I've included the relavent quote for those too lazy to read the links I provided.

"A common question regarding unregulated systems is whether they can be run without connecting the motor to a battery without damaging the stator-rectifier. The answer is that it depends. Some motors can be run without batteries, and some can't. Follow the recommendations in your owner's manual. Some manufacturers provide caps to cover the battery-cable terminals to prevent them from touching while the engine is running without a battery. However, some companies, Mercury for example, also recommend disconnecting the stator wires from the rectifier and insulating them from each other if you're going to use their motors without a battery."

(source)

Author: Ed Sherman - professor at the New England Institute of Technology and author of 'Outboard Engines'. He _wrote_ and teaches the American Boat and Yacht Council's certification program for electrical technicians.

I dispute my own credentials (  ), but you wanna dispute _those_ credentials go right ahead.


----------



## erps (Aug 2, 2006)

So did you wreck it or not? I had an old Honda outboard with a two prong connector to charge a battery and it didn't hurt anything to run it disconnected. That was a long time ago through (1970's?) and your outfit sounds a lot newer (easier to screw up).


----------



## TohatsuGuru (Oct 3, 2007)

The short answer is no you will not damage that model of Yamaha as it does not have a voltage regulator. Engines that do have voltage regulators will burn out the regulator and rectifier.


----------



## tenuki (Feb 11, 2007)

whoo hoo!

But I'm installing a battery this winter anyway, gotta add nav lights, I love night sailing.


----------

