73 Evinrude 85 hp. Ran great all morning until I ran the first gas tank dry. I swapped tanks and it fired for a few seconds then died. Wouldn't restart. The starter would fire but not enough juice to actually spin the motor. Tried to pull start it. No way. At the time the battery was reading 12.4v but dropped to 4 on key on. Terminals on the battery were loose.
Long story short, a good Samaritan charged the battery on his truck for 20 min and she fired right off. Voltage was 12.9 at idle but falling slowly.
What should the output be at idle? Anyone want to explain stators and rectifiers since there's no alternator? Will one keep running if the cables are too loose to charge?
I don't know anything about outboard motors, but I know Harley charging systems, which use rotors, stators and a regulator. If you pull the wire where the regulator plugs in, check the resistance to motor ground on each of the pins (if there are 2). There should be no continuity. Check the resistance between the 2 pins. There should be low resistance (like a few ohms). Start the motor and measure the AC output. Should be probably around 20V at idle, give or take. If it does all that, your regulator is likely fried.
The basic procedure should be similar to what I outline here:
http://www.hdforums.com/forum/evo-classic-models/876288-how-to-diagnose-your-charging-system.html
well there is one called Super and the other called turbo.
jstand
HalfDork
8/22/16 11:14 p.m.
You will need to get a shop manual, or clymers or Haynes. Many engines that run a stator/rectifier system won't charge unless the engine is spinning faster than idle (possibly 1500 or more).
The specific rpm and output is something that varies with mfg and model, so you need a shop manual to get the right info for testing.
If the voltage rises and continues to rise above 14volts as the rpm increases then chances are the regulator is bad.
If you don't have any shorts, but the voltage (DC) doesn't increase at all with rpm, than the rectifier is probably bad.
The charging system probably isn't too strong, so a weak battery combine with poor connections will likely result in starting issues.
I'd start with good battery, a fresh charge, and maybe bring a jump box. See if the battery holds up over the course of a day. If is maintains its charge over a day on the lake then I'd say that is enough to show the charging system is good.
Generically, it's a stator winding mounted rigidly under or around the flywheel on top. The flywheel has magnets. The spinning of the flywheel creates the fields that create the juice.
Rectifier and regulator are mounted elsewhere, and may be combined or not. Depends entirely on the manufacturer, and I don't know old Evenrudes enough to comment or suggest which way it may be.
Corrosion is the normal failure throughout the copper wiring for an outboard electricals. As well the connectors. But, with many an old outboard, I've seen the stators fail simply because of corrosion up through everything. Be very cautious with used replacement parts for this reason.
Thanks for the insights guys. I'm hunting down a manual now. So far I've learned that the motor is old enough that it is unregulated, rectifier only, and that it doesn't really charge much even when working correctly and at WOT. I've also learned my battery is like half the recommended Ah capacity.
I suspect that loose battery cables and about 45 min of idle cruising just before the incident combined with a too-small battery put me just below enough juice to fire it. I'm going to pick up the correct battery, check the rectifier, and then carry the small battery as a charged spare. I'll probably wire it in on a selector switch as a backup eventually.
Oh, and nylock nuts on the battery posts so they don't vibrate loose. And the phone number of the park rangers in my cell phone....
Thanks for the insights guys. I'm hunting down a manual now. So far I've learned that the motor is old enough that it is unregulated, rectifier only, and that it doesn't really charge much even when working correctly and at WOT. I've also learned my battery is like half the recommended Ah capacity.
I suspect that loose battery cables and about 45 min of idle cruising just before the incident combined with a too-small battery put me just below enough juice to fire it. I'm going to pick up the correct battery, check the rectifier, and then carry the small battery as a charged spare. I'll probably wire it in on a selector switch as a backup eventually.
Oh, and nylock nuts on the battery posts so they don't vibrate loose. And the phone number of the park rangers in my cell phone....
edit: here's a pic, just because
http://boatinfo.no/lib/evinrude/manuals/1973-1991johnsonevinrude.html#/0
yeah, I've been reading that. I think I'll still get a hard copy for the shop though.
The rectifier test procedures seemed a little confusing, but it probably makes more sense when you're actually looking at the motor.
