'85 115 Johnson not charging

[surrender]

Ok, so today was the first time with new/old motor running with new Lowrance 339 GPS. On the GPS I was watching the voltage because I suspected a charge problem. Started out with a brand new battery and when I left the ramp the voltage read 12.1. At cruise speed(3900 rpm) voltage got as high as 12.5 and while trolling the beach the voltage stayed between 12.3-12.4. This was with the GPS/sonar screen brightness on the middle level, and while using the trim motor and bilge pump every now and then. If I brightened the screen the voltage dropped to 12.0-12.1 instantly and held there. At those voltages motor can be shut off for long periods and I drifted the bottom with the sonar on and when I went to start up, no problems. I did some test in the driveway and I cant tell if the problem is in the stator or the regulator. I disconnected the yellow wires coming from the stator and tested them with the motor running and I got nil or close to it. Even wired my old litle three wire rectifier to those wires and I get no voltage at the red wire coming off the rectifier. I am thinking the charge circuit off the stator is not putting out, but my tach works.

 

[schematic]

Re: '85 115 Johnson not charging

I disconnected the yellow wires coming from the stator and tested them with the motor running and I got nil or close to it. Even wired my old litle three wire rectifier to those wires and I get no voltage at the red wire coming off the rectifier. I am thinking the charge circuit off the stator is not putting out, but my tach works.

Are you us the a/c setting on your meter when testing the yellow wires for voltage?

 

[surrender]

Re: '85 115 Johnson not charging

Thanks for the reply, yes I was looking for ac voltage as this would be before the rectifier/regulator. I built a homemade DVA adapter but didnt use it this time. Think I may break it out and do some more testing. Anyone else with any thoughts please chime in

 

[emdsapmgr]

Re: '85 115 Johnson not charging

If your engine has tilt/trim, the engine will have a combination rectifier/regulator. Normally after you run the engine for 15 minutes on plane, the battery volt gauge should increase to around 13.5 volts and hold there. If your engine does not have power trim, the engine will have a rectfier only. After running for a while, the battery voltages should approach 16+ volts. Since the charging system also sends the signal to the tach, it is usual for a charging problem to also be visible in the normal functioning of the tach. You have not mentioned any tach problems....

 

[surrender]

Re: '85 115 Johnson not charging

Sorry for the delayed reply. No Tach problems. Motor does have the top mounted reg/rectifier so I was thinking about 13.5 or so should be seen after running but the most I get is 12.4 while running.

 

[metriccrescentwrench]

Re: '85 115 Johnson not charging

the most I get is 12.4 while running.

You get this value from your GPS?

Does the voltage stay in the same range all day? From your first post it sounds like that's the case, and if so you may not have a problem. Measure the voltage right at the battery with the engine running using a good multi-meter and see what you get. I suspect that you're seeing a reduced voltage because of the voltage drop between your battery and the GPS.

 

[surrender]

Re: '85 115 Johnson not charging

Yes voltage observed is from GPS. Dont think its charging because voltage does not go up when I run for long periods at 4000rpms and if I run my GPS on the brightest screen the voltage drops to 12.1 or so and does NOT come back up while running. The draw from the GPS is very small and the charging system should be able to raise the voltage while running. Thinking stator charge coils.

 

[metriccrescentwrench]

Re: '85 115 Johnson not charging

Just do yourself a favor and check the voltage right at the battery with the engine revving. Unless your gps is wired directly to the battery it's not a good indicator of battery voltage because there will be a voltage drop due to the current draw of everything else that's on the circuit. Just for instance, I've got a Humminbird side imaging unit - I pull power for it from a circuit at the driver's console, and I also have a panel mounted digital voltmeter wired directly to the battery. When my voltmeter is (correctly) showing around 14 volts at the battery my Humminbird is only showing a little over 12. It's possible you do have a problem, but it would suck to start replacing expensive components without knowing for sure what's going on. (I'm a EE - don't make me start doing math and citing Ohm's law ).