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1980 115hp Charging Issue

bill_w

bill_w

Advanced Contributor
Hi. I've got an 80' 115 hp Johnson. I'm not sure if the charging system is working. I've installed a voltmeter on the dash, and it's slowly working it's way down to about 11.5 volts. I've charged the battery, the meter reads just over 12 volts. The tach works, and I've been told that if the tach works, the system is charging. There is nothing installed on the boat that has power to it all the time, only when the switches are turned on (bilge pump and lights).

thanks,
Bill
 
At the most, it's about a 9 ampere or so charging system.

Engine NOT running, hook up a volt meter across the battery, note the reading. Now, start the engine and put into a fast idle, note the reading again which should have increased slightly.

And the tachometer operates off of the charging system, so yes, if the tachometer works, the charging system is working also.
 
Thanks for the info Joe. Maybe I just have a bad battery, that's not holding a charge. I'll try changing it over to a different one.
 
A test with the engine NOT running.

You might want to check for a battery drain also. Have the cables/wires disconnected from the positive post of the battery, then connect a ammeter or sensitive volt meter between the positive battery post and the cables/wires.

If there's a drain, it'll show up on the meter.
 
I'll try that this weekend. Unless there is a short somewhere, there should be no current going anywhere. The only electrical accesories on the boat are the lights, bilge pump, trim and fuel gauges. The fuel gauge is wired into the key switch for power, same as the tach and trim gauges.
 
Joe.. Sorry it took so long to reply. Never had a chance to check it until this weekend.

1. Battery voltage does not increase with the motor running. The battery was almost dead, so I charged it to get it running. Charged for about 4 hours at 10 amp, brought the volts up to 12.4. Ran it on the lake for about an hour, pretty much all full throttle, volts decreased to about 12.2 (I left the VOM hooked up when running the lake). I figure the power went down from using the trim. Tried to restart it at the dock, no way, turned over twice, then dead.

2. There is a drain on the battery, somewhere in the light circuit. When I disconnected the wire for the lights, and tried it with the VOM from the + post to the wire, I got 11 volts. So, not a direct short, but a short just the same. Nothing on the bilge pump circuit.

So, the tach is working, but not getting anything to the battery. Any ideas where to start looking?

thanks in advance

Bill
 
on the light question first.....is the light switch on or off?....are lights permanent or plug in as needed?....did you disconnect the light wire from the positive post....where is the light switch in the circuit?..in the hot side going to the lights or the ground side? its also possible you have a bad battery..a fully charged battery should read 12.7v after you charge it and disconnect the charger....this charging can take 24 hours or longer depending on the charger...its also possible that you have a high resistance connection to the battery...either in the wire itself(normally right at the terminal) and you are dropping the charging voltage across this resistance or a dirty post/wire connection...see if you read the same voltage right on the rectifier output that you do on the battery....do this with the motor running about 2k rpm as you will not have a voltage drop if you are not drawing current..plus you want to verify that the rectifier is putting out a charging voltage....its also possible that the grey wire has been moved to the stator output and is not using rectifier output...i would address the battery charging problem first and then make sure of the light drain question...
 
You may just have a broken rectifier.... I had that prob with my 75hp Evinrude...
Check if the all the diods are still allright, Joereeves knows how to wire them up.;)
 
bill_w said:
So, the tach is working, but not getting anything to the battery. Any ideas where to start looking?
Click to expand...

Sorry but I don't understand the question..... (not getting anything from the battery?)

(Small Rectifier Test)
(J. Reeves)

Remove the rectifier wires from the terminal block. Using a ohm meter, connect the black lead of the ohm meter to the rectifier base (ground), then one by one, connect the red lead of the ohm meter to the yellow, yellow/gray, then the red wire (some rectifiers may also have a fourth yellow/blue wire. If so connect to that also). Now, reverse the ohm meter leads and check those same wires again. You should get a reading in one direction, and none at all in the other direction.

Now, connect the black lead of the ohm meter to the red wire. One by one, connect the red lead of the ohm meter to the yellow, yellow/gray, and if present, the yellow/blue wire. Then reverse the leads, checking the wires again. Once more, you should get a reading in one direction and none in the other.

Note that the reading obtained from the red rectifier wire will be lower then what is obtained from the other wires.

Any deviation from the "Reading", "No Reading" as above indicates a faulty rectifier. Note that a rectifier will not tolerate reverse polarity. Simply touching the battery with the cables in the reverse order or hooking up a battery charger backwards will blow the diodes in the rectifier assy immediately.
 
Too late Joe...I spent Sat trouble shooting, with the engine running, I only got battery voltage at any connection I tried. For the hell of it, and because I had one, I swapped out the rectifier. Problem solved, battery now charging. I am confused though, because the tach was working, I was under the impression that the charging system had to be working. I did try two rectifiers, one I thought was good, and one was new. The first one was was trash, no charging, no tach. New one works.

So, why did the tach work, with a bad recifier? Only one diode gone maybe?? I didn't test it, just changed it. I know this is an unregulated system, so is 15.5 volts OK when running WOT?

thanks,
Bill
 
Why the tach was working? Hmmm, how about poltergeist? Strange.

A lot of those unregulated systems hit 16 volts... a litttle high but not much one can do about it.
 
the tach grey wire may be hooked to stator output instead of the rectifier output...have you had the motor since new?
 
after you put the boat in the water and run it on an extended run of 45 minutes to an hour you may the see the charging voltage creep up as joe mentioned....it depends on the type and age of the battery....these unregulated charging systems do that with a sealed or a jell battery..they will do that with a good marine battery also...16-17 volts will eventually blow the rectifier again....when it starts to go you will see the tach(if wired correctly) start to vary and your meter down to battery output...both intermittent until the rectifier is blown...this will not effect motor performance.....just the tach and no charging...no need to cut short a fishing or whatever trip....just be aware that you are not charging the battery...
 
No, I'm the third owner of the motor. Looking at the terminal board, everything is in agreement with the terminal cover plate. I don't see anything that might have been molested/changed. In fact, every terminal is still covered in the factory waterproofing goop. Interesting that with the 'bad' rectifier, I had no charging AND no tach. So, whatever was causing the trouble was cured by the rectifier swap. The battery is new this June, and is a good marine type. Time will tell how long the new rectifier lasts.
 
Well, the rectifier didn't last long. Blew it out this weekend, so I got about a days use from it in total. The tach quit this time too. I finally got the factory manual for this motor, and the schematics show a regulator!! And, it is on the motor!! Is the regulator supposed to keep the charge from going over 14 volts? Is there a way to test the regulator? I do have another regulator for this motor that came off another 115. The charging gauge I have connected shows about 15.5 volts at 5000 rpm. If the regulator can't be tested, I'll just try the other one, unless 15.5 v is normal.

thanks in advance
Bill
 
14.8 is actually the top end of what you want to see on that voltage if its coming from a regulator.......i am confused now on what rectifier is blowing...you say you have a regulator and you also said the terminal strip still had the gunk on it and had never been disturbed...is the rectifier you are blowing mounted on the engine block on the left hand side as viewed from inside the boat?is the regulator mounted on top of the engine just back of the flywheel?which one is wired in?
 
just reread the problem...you state the battery is new and a good marine one.....if you are running a rectifier only charging system this is probably your problem....wire in one of the regulators that you have...
 
The regulator is wired in..its on the top of the motor, on the right hand rear side looking at the motor from the front. It is NOT the water cooler regulator/rectifier used on later models, but just a sorta pointed rectangle shape. There is a seperate rectifier on the left hand side, mounted in front of the terminal strip. According to the factory manual wiring diagram, this is the correct set-up.

Maybe the regulator isn't doing its job? I do have another one, from a motor that I converted to a water cooled regulator/rectifier. Maybe I should just try bolting that one on??
 
Strange that rectifer blew like that. I've seen unregulated engines reading at about 16.8 volts on a daily basis but it never effected the rectifier. Loose wire somehere?
 
A loose wire where? From the rectifier..no. No where else on the motor, all the terminal screws are tight, a good ground on the rectifier. Before it went totally, I noticed the tach was reading about 3000 instead of 5000 at WOT. Pulled into the dock, shut it down for a while. Went back out, all was normal. Later on, tach quit totally, and that's when I got the VOM out and checked for charging.

Maybe just a defective rectifier?
 
i think a lot depends on the battery joe..a regular marine or car battery of yesteryear had an internal discharge that would take care of a lot of overcharging....the jell and the maintenance free batteries do not have that...a good regular marine battery will give problems with blowing the rectifier also..i am speaking of the marine battery that the parts stores sell...they will take an overcharge which is not good on these rectifier only systems...i have an unproven theory on that....because the charging voltage is actually not a flat dc but has pulses i think the peak of these pulses actually gives a slight reverse polarity on the rectifier at some point as they get higher...regardless of that a reading of 16 and above will eventually knock out the rectifier...it may take a year or more or it may happen back to back on new rectifiers...the dead giveaway is when the tach starts cutting up....you can bet the rectifier will fail sooner or later...the best fix is the regulator that fits right behind the flywheel on top of the motor...the holes are probably already there to mount it..if you wish to just replace the rectifier get one from radio shack at a fraction of the cost...the good thing about the problem is the rectifier is the only part that will fail...i have never saw a stator winding damaged from the problem...
 
i would add a voltmeter to that boat....a speedometer i could care less about on my boat but the meter and tach i got to have...and dont load the starting battery down with a lot of accessories.....the rest of that jazz if you got it goes on the trolling motor battery...avoid grounds and ground leaks and shorts etc on the main battery......to me just the engine and its required power and the charging circuit only off the main is the way to go...maybe a bilge pump...
 
A voltmeter I do have. Only have lights, bilge pump on the boat. Tach, speedo, trim gauge, fuel gauge, voltmeter. Thats it, thats all. And are you talking about the watercooled reg/rectifier, that mounts into the block behind the flywheel? Just have to pull off the lifting hook, and the watercooled unit fits into that hole.
 
FYI, as you already found out the rectifier can be bad and the tach still work. There are 4 diodes in a full wave bridge rectifier which you have. It depends on which diode goes and how it goes (shorted or open) as to how it affects the system. And never connect electronics to the trolling motor battery. When you step on the go button for the motor there is a surge while the motor gets to speed. Electronics do not like surges.
 
inbfshn....i stand corrected....i been running a stripped down boat so long i forgot about the fishfinder etc...yes i am talking about the watercooled one bill...
 
For the time being, I'm going to try running the new air cooled rectifier that I have. I may try switching out the regulator for the other one I have. If it goes again, I'll save my pennies over the winter for a water cooled regulator/rectifier.

thanks guys
Bill
 
Well, the new rectifier didn't last long. I have probably only run the motor for an hour, if that, since I put the new one in. Had the boat out today, the tach started acting up, but the volt meter is still running about 15.5 volts. So, the rectifier should be toast next time I take it out. I still don't understand what the purpose of the regulator is, since it's obviously not doing anything. Maybe I should swap that out too.
 
Well, I got fixed it this weekend. The voltage reg was bad. After partially blowing the last rectifier (the tach went wonky, battery still charging), I took it for another run with a good VOM hooked up. It was charging at about 16.5 volts. I swapped the regulator for another one I had, now it's down to 14 volts max. Now here is a really dumb thing I noticed while pricing out parts. To buy another original votage reg, it's about $172.00 But, to swap out the system to a block mounted water cooled regulator/rectifier, it's only about $73.00. So, I know what I'm doing the next time the rectifier goes, because they are about $35.00 each.
 
bill_w said:
Hi. I've got an 80' 115 hp Johnson. I'm not sure if the charging system is working. I've installed a voltmeter on the dash, and it's slowly working it's way down to about 11.5 volts. I've charged the battery, the meter reads just over 12 volts. The tach works, and I've been told that if the tach works, the system is charging. There is nothing installed on the boat that has power to it all the time, only when the switches are turned on (bilge pump and lights).

thanks,
Bill
Click to expand...


I have a 28 HP 1989 johnson that i just replaced the rectifier in because the battery was not charging.. (very happy it was not the stator) anyhow it is charging again but im getting an intermediate voltage drop i will be running WOT and watching the volts on my depth sounder go up then all of a sudden it will drop back .4vdc then back to where it was.. its almost like im turning something on then turning it off.. can a new rectifier cause this? or do i just have a wire touching somewhere in the system.. or a high resistance connection somewhere?? it really seems like something is drawing of the battery but not at all time like i said its intermediate.. thanks in advance
 
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