How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293R

[rs2k]

I just replaced the rectifier on my 1972 100HP Evinrude 100293R. When I pull the battery cables off the engine while it's running it shuts off. I was told that this engine needs a battery to run though. Is there another way to tell if the engine is charging the battery?

 

[BaitThrower]

Re: How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293

Grab a multimeter and check the battery with engine off, and then when engine on. If its showing higher voltage with engine on, then engine is charging battery. For normal electrical chargers, usually they charge 12v batteries at around 13.6-13.8v, so this is the reading you might get on a multimeter when you put the multimeter probes on the battery terminals while it is plugged up to the charger.

Not sure what voltage your boat engine sends through the rectifier, but I'd imagine it would have to be something around those figures?

 

[F_R]

Re: How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293

You pulled the battery cables off while it was running??? Congratulations, you probably just ruined your new rectifier. You are lucky you didn't ruin the pulse pack too. Never do that, in fact make sure the connections are clean and tight or the same thing will happen.

 

[HighTrim]

Re: How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293

When I pull the battery cables off the engine while it's running it shuts off.

I have to admit, that is the first time I have read of someone attempting that on here! Question is, why?? lol

As Frank stated, that is a bad idea. Test your rectifier, although I can pretty much guarantee that she is toast. You likely took out a single diode, cross-polarizing is even worse, and takes out both sides of the bridge rectifier right away.

Installing a volt gauge will tell you while underway that all is well with the charging of the battery as well. Although, as stated, a multi meter will quickly tell you if she is being charged.

 

[R.Johnson]

Re: How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293

FR: I did'nt even have to read your come-back on that one. Let's see! where are my direction's?

 

[jay_merrill]

Re: How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293

usually they charge 12v batteries at around 13.6-13.8v, so this is the reading you might get on a multimeter .... Not sure what voltage your boat engine sends through the rectifier, but I'd imagine it would have to be something around those figures?

I have a voltmeter installed in my boat & the engine is a 1972 65hp Johnson. The values that you describe are just about what I see on the voltmeter. The needle will show voltage (+- 12VDC) as soon as I move the key to the "on position" and will jump up to the mid/high 13 volt range once the engine is running.

Also, I never switch batteries once the motor is running for the very reason that the guys mentioned. From what I understand, even that split second lapse in connection between one battery and the other, can do nasty things to a rectifier.

 

[Vic.S]

Re: How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293

pulled the battery cables off while it was running

With luck it won't have damaged the rectifier if the engine was only idling as the output volts probably would not have been high enough for there to have been any charging current flowing. It is when a good current flow is interrupted that you get a big surge in volts that can damage the rectifier. Suddenly all the electrons whizzing along have nowhere to go and all pile up like a major pile up on the freeway.

If in any doubt it would be wise to check the rectifier as described in the Engine FAQs as it is possible that one half is blown while the other is good. That will give a low charging rate but will be difficult to assess.

If you use a digital meter for rectifier testing use its "diode test" setting if it has one otherwise the highest ohms range. No problem with old fashioned analogue meters but there is with many/most digital ones

 

[karlow1]

Re: How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293

Right! like they said.
Next time for any type of engine it's simple.
Get a DVM and measure the battery voltage with the engine off.
Then start the engine, is the voltage higher?
If not rev it up a little (maybe 1500-1800 RPM). Is it higher?
If the answer is no, or maybe break out some bucks! The correct answer
is it should be up by well over a volt from 12-13.5 up to 13.5-14.5 Vdc.
If it's hitting 17Vdc, you have a over charging problem!

Now you know.

 

[rs2k]

Re: How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293

I never knew that would hurt the rectifier. I've done that same check on automobile alternators without anything bad happening. I figured the rectifier would be able to run the ignition in the event that the battery failed. I guess I was wrong. I'll check the rectifier.

 

[Vic.S]

Re: How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293

I never knew that would hurt the rectifier. I've done that same check on automobile alternators without anything bad happening

Its a well known problem with inboard engines when people switch from one battery bank to another. You were probably lucky and doing it at idle speed when there was little output from the alternators. When people switch batteries on inboard boat engines they will often be doing it at cruising speed. They should switch the new bank on before switching the old one out but every so often they get it wrong.

Some alternators have a surge protection diode anyway, although it cannot be relied upon and may only function once.

 

[R.Johnson]

Re: How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293

If you are going to switch batteries while the engine is running , you need a make before break switch.

 

[rs2k]

Re: How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293

I cannot find instructions to test the rectifier. What is the procedure?

I did the disconnect at idle speed.

 

[Vic.S]

Re: How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293

Finding topics in the Engine FAQs is sort of initiative test for Newbies. You failed but as a veteran of 14 posts you should not have done

Go to the "Repair and Maintenance" index by clicking the link at the top of the page. The first item on there is "Engine Frequently Asked Questions" go to that and look for "Small Rectifier Test, by Joe Reeves ".

If you still cannot find it go to dunces corner or CLICK THIS LINK

I think yours is one with three yellow or yellow + stripe wires.

 

[Vic.S]

Re: How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293

If you are going to switch batteries while the engine is running , you need a make before break switch.

Off topic but people like use those rotary "1, 2, off, both" switches but sooner or later switch via the "off" postion rather than the "both" position.

 

[rs2k]

Re: How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293

Aha! I was looking under "Evinrude Outboards" under "Outboard Motor Topic" under "FAQ"


I just replaced both starting cables with new 2-gauge (overkill) cables. The old cables looked like 6-gauge orginal cables from 1972. The old cables were very corroded. The first time I tried to start this engine I got smoke from the cables. The rectifier I took off the engine was visibly shorted out. What's the chance that I also have a bad stator? Does the stator do anything to run the ignition or is it just to provide current to the electrical system?

 

[F_R]

Re: How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293

On that motor, the stator only charges the battery. AND it supplies current to the shift system through the "monkey nutz" diodes. If those diodes are blown it can cause the alternator not to work. There is also a clipper circuit that "clips" voltage spikes. Actually, that clipper circuit may have saved your rectifier.

 

[rs2k]

Re: How can I tell if my engine is charging the battery? - 1972 100HP Evinrude 100293

After putting the rectifier back on and running the engine on the lake I have a new problem. Now the engine is over charging the battery. I need to run around with the running lights and spotlight on now. Everything appears to be working as it should, though!

Thanks!