TOPIC: Dead battery, stuck on the lake

73 Evinrude 85 hp. Ran great all morning including turning it off and restarting once for a lunch break and once for a beach break. Then we slow cruised for a while until I ran the first gas tank dry. I swapped tanks and it fired for a few seconds then died - not surprising since I'd run it out of fuel. Then it wouldn't restart. The starter would fire but not enough juice to actually spin the motor. Tried to pull start it. I got one or 2 good spins but no start, then it seemed like the resistance turning the motor went way up. No way it was pull starting then. At the time the battery was reading 12.4v but dropped to 4 on starting. Terminals on the battery were loose so I tightened them down but it didn't help. I had been running a fish finder the whole time too, and occasionally getting false shallow warnings, so I think the loose cables were causing some issues.Engine was warm at the time but cool enough I could turn the flywheel by putting both hands on it. I couldn't keep them there more than 5 or 6 seconds, but I don't think it was overheated at all.

Long story short, we drifted to a dock and 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. Ran great back down the lake to the dock and trailered up.

What should the output be at idle? Will one of these run with the battery disconnected once it's running? Will one keep running if the cables are too loose to charge?

Anyone want to explain stators and rectifiers since there's no alternator?

I don't think they run without the battery. I was running my '74 70 hp and kept having stalling issues when it would hit a wave. Eventually it totally stalled out, and would not start!

Turned out to be loose battery cables, and it ran like a champ the rest of the day. Lesson learned!!

As for stator / rectifier, you are speaking of black magic of which I know nothing! Better wait for one of the gurus to come to your rescue.

BTW - I almost hardly hit the water without a jumper pack in the boat. More than once I have seen Mr Murphy pop his head into a boat and kill the battery. No much fun trying to pull start something designed for a starter. Cheap insurance for a day on the water. And my buddy recently showed me a Lithium Ion pack about the size of a box of checks - he said he used it to start a totally dead Chevy V8! Should be plenty to start an outboard, and it could fit in the glovebox.

Sounds like the rectifier is bad. But you'll need to disconnect the stator wires from the rectifier and check the resistance of the coils under the flywheel, to make sure they're not burnt out.

9 times out of 10 it's the rectifier/regulator assy. I can't recall if the old Johnrude V4's had a regulator built-in, but either way the voltage should rise when the engine is revved above idle.

As a note of caution, never rev a V4 above 2000 rpm, it's bad for the long-stroke engines.

I found the diagram for your motor, looks like it has the old 3-wire rectifier assy that's pretty cheap:

www.marineengine.com/parts/johnson-evinrude-parts.php?year=1973&hp=85&model=85393M&manufacturer=Evinrude§ion=Ignition+System

Part #33 on the diagram.

So, the 2 yellow wires that connect to the rectifier are the stator wires, just disconnect them, hook an ohmmeter to them on low-ohms scale and see if you get a reading. It'll be a fairly low value.

A "backyard diagnostic" technique is to move the flywheel by hand about 1/4 turn or so, as soon as you start moving it, the meter reading will change. That's a good indication that the charging circuit coils are working.

I've attached a Merc rectifier test, should be the same procedure on your Johnrude 3-wire rectifier. Note that on your rectifier, the (2) yellow wires are the "alternator" connections for the purpose of the testing procedure.

HTH......ed

I like to carry a kicker motor on a boat thats big enough to have it. A small pull start motor will save the day more often than not, as long as its reliable.

Even a little 2hp honda will move a smallish fiberglass speedboat fast enough to have good steering and control.

Def helps if the kicker will run on the same gas as the main motor too.

excellent info ed! I'll throw the meter on it this weekend. If I replace the rectifier, what's the consensus on a standard rectifier vs a regulated one?

Once started the motor runs fine. Really well, actually. I'm thinking right now a spare battery is cheaper than a kicker motor. Plus it's on a 15' trihull so there's not much room and I'm already heavy on the transom with the big motor. I was carrying a 30lb thrust trolling motor, but with the battery already low it was useless. Not sure it would have done anything much anyway. We also have good wood oars. They were enough to maintain control but getting any distance down the lake would have been hard. She ain't a rowboat.

I also found some literature on the motor that recommends a minimum of a 70Ah starter battery. The one that came with the boat is new but it's small. Hard to find specs on the Everstart batteries, but my guess is it's about half the recommended capacity. I'll probably buy a new dual purpose battery over 70Ah and carry the small as a charged spare. Eventually I'll probably wire in a selector switch and keep it connected.

We're running small lakes right now so the consequences of a breakdown aren't that severe. I'd rather work out some redundancy on the critical systems now so I'll have it in place if we venture further afield.

You could get one of these cheap eBay Briggs & Stratton garden tractor voltage regulator/rectifiers for a cheap upgrade from a standard rectifier:



Less than $14 shipped and these are rated for up to 16amps, your V4's charging system puts out around 10 amps IIRC.

One of the Merc dudes at John's Old Merc forum says that he has one motor running with a Briggs V/R and the other with a Merc unit, has noticed no difference in operation or durability.

Your battery and any sensitive electronic equipment will like the regulated voltage much better, and will probably live longer. All you have to do is figure out a way to mount it! Bullet connectors are plenty good to handle the rated current.

Briggs makes a mating wiring harness for the unit, if you really want to get fancy:



Cheers........ed

Awesome!

I guarantee I can figure out a way to mount it - I'm a certified Zip Tie Wizard. Wiring it's easy enough too, I would probably solder & shrink on connectors to match the 'Rude's oem.

Thanks for that link!

Zip-ties would do the job but in that case, be sure to run a separate ground wire from the case to the block!

The metal case provides the ground path for the unit.

Good note on the ground. I would have missed that.

I ran the quick backyard check when I got home from work yesterday. 3.1 Ohms on the rectifier and definite resistance changes on the stator when moving the crank. Maybe I won't need to replace anything and it was just loose connections. I'll do the full check procedure from the repair manual and a running voltage check on muffs this weekend.

I finally got a chance to do the rectifier testing. One yellow wire is open circuit both directions and the other is dead short both directions.

Briggs rectifier/regulator ordered, Out for less than $20 even with the expedited shipping. I'll post a few pics once I get it and adapt the mounting.

I mounted the Briggs and Stratton rectifier and regulator basically in the same place as tas the old rectifier. The case should be grounded as it's bolted down against the engine casing, like the old one. I cut off the B&S connecters on the wires and added ring terminals so it's easy to make the connection on the factory screw terminal strip . I had tot add a short extension to the red wire, it wasn't quite long enough. Two yellow wires were attached in the same place as the previous yellow and yel/gray wires, and the red wire was attached where the purple wire was.Buttoned everything back up and tested it running on muffs. I've got 13-14 volts DC at idle (measured at the battery) and as the engine warms up it goes up. Once warmed up, I saw easily up into the mid 15 volt range and climbing at higher RPM. FWIW, I'm also seeing about 30v AC at the battery as well....

At least I'm getting charge voltage, but I thought this thing was supposed to regulate the voltage? Did I hook something up wrong? Is it just a bad regulator?

Here's pics of the old and the new:






I'm headed out on the lake tomorrow morning. I figure it's no worse than the factory unit was with no regulator, but it's pretty frustrating.

It's certainly possible the regulator part isn't working.

At least it's charging, so you're no worse off than before your old rectifier quite.

I wouldn't worry about that AC component, probably a fluke on your meter,
or a "ghost" reading because of the waveform of the pulsating DC output of
the rectifier.

Given the feedback from the other forum, the darn thing should have worked, though.

ultraclyde wrote:

Anyone want to explain stators and rectifiers since there's no alternator?

Your motor has a 6 amp stator that will put out it's rated current at approx. 3000 RPM and above. The output is AC current that may well be up to near 20 volts AC if you disconnected the yellow leads & hooked a volt meter up to them.

The rectifier (it is not a voltage regulator or regulator/rectifier, it's just a rectifier) takes the AC current and thru the use of diodes turns it into DC that goes to the battery for charging.

So, AC in from the stator via the 2 yellow wires and DC out to the battery thru the red wire. No way to control the voltage & it is possible to overcharge the battery with extended high speed running. The following is taken directly from the '73 service manual, page 7-9..... OVERCHARGED BATTERY, cause=Extensive running without accessories, what to do=Turn on some accessories during extensive running.

I should add that a CONVENTIONAL alternator is the above system all contained in one housing that we are all familiar with. Most alternators (except for the earliest ones) also have the regulator internally. The primary difference is that in this (outboard) application, the magnets are a fixed strength, thus the output can't be regulated. Excess current is burned off to ground thru the heat sink in the regulator. In the CONVENTIONAL alternator, there are no magnets. The rotor creates a variable strength magnetic field because the regulator gives a variable strength exciter current to the rotor. This is how the alternator output is controlled.

63LStriton wrote:

I don't think they run without the battery. I was running my '74 70 hp and kept having stalling issues when it would hit a wave. Eventually it totally stalled out, and would not start!

Turned out to be loose battery cables, and it ran like a champ the rest of the day. Lesson learned!!

Actually, I see no reason the motor won't run with a dead or disconnected battery.

Well, she ran great on the lake for about 4 hours. I don't have an onboard voltmeter (or a tach for that matter, both will be future add-ons) so I don't know how much it was actually making. We beached once, anchored out for lunch, and then shut down when I ran the first tank down. Cranked right up every time.

After the anchoring experience it's pretty clear the 13lb mushroom that came with the boat isn't the right anchor. I'm going to pull the fluke anchor with chain out of my small sailboat and try it instead. Probably keep the mushroom on board as movable ballast and a quick sandbar/shore anchor.