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40EL75C Stator and Rectifier Woes

L

leogallant

Member
Hi guys,
Was out shrimping on Wednesday and I noticed the FishFinder went off about 1 hour into our trip. 20 minutes later I had turned of the motor and when I went to start it up, not enough juice in the battery.

After getting towed back by fellow shrimpers (whew!), I've been going through my mind what happened. First clue is the fish finder going out, as I've read they are the first to go when there's low voltage.

I've tried testing the stator and rectifier:

TESTING RECTIFIER(Evinrude part #
0581778)​
: I start up the motor (was able to recharge battery no problem - eliminating bad battery issues), I have the red wire from Rectifier detached from bus block. With multimeter set at 20V DC, I ground the black lead to engine, and put red lead on the red wire from rectifier. I only get a reading of .63 Volts DC and I'm guessing it should be reading at least 13 Volts DC, right? This tells me either the Rectifier is bad or the Stator is not supplying enough voltage and is bad.

TESTING STATOR(Evinrude part #
0581252)​
: I'm not quite sure how to test voltage. With engine running, I believe I'm supposed to get between 250 and 300 Volts AC from each of the 3 wires coming from stator? Where should black lead go and where should red lead go? There are 3 wires from the stator: yellow/blue stripe, yellow/white stripe, yellow. Also, having no luck testing resistance, set multimeter to 200 Ohms, and touch black lead on one wire with red on another until you've touch the combination of all 3 wires from stator, but I'm getting no reading...

Thanks!

Leo
 
Update on Ohm Resistance test on Rectifier: Multimeter set to 2K Ohms
Red lead to Ground(case of rectifier), Black lead to each of the 3 yellow wires yields in the .640 range on each wire.
Reverse the wires and no reading which indicates the diodes should be working correctly (one way only).

Does this sound like a good rectifier and if so, I'm guessing I need a new Stator?

Thx!

Leo
 
That sounds like a good rectifier, but on occasion the can break down under load and trick you, but that is rare! They normally read open one way as you reverse the testing polarity as you have seen. You should have more voltage output from the alternator. Make sure your meter is set to ac when testing the alternator or you will get a low reading!
 
put the red wire back on the terminal strip...have a good charged battery hooked up for normal operation...set the meter to 20v dc scale..take a reading from the red wire to ground...record this...then start engine and run at about 1900-2000 rpm...take the same reading and record it...it should be higher than the original no running battery reading....if it is not set the meter to ac and with the motor running take a reading between the yellow wires coming from the stator..record this and please get back to us....
a couple of questions...have you had the boat for a while and know that it was charging before?..has there been any additional wiring added recently?any device added etc?do you have a tach and voltmeter on the boat?
if you took resistance readings correctly then you have a bad stator....but thats an expensive item to replace without making sure...
look under the flywheel and see if you can see any melt from the covering on the stator...dont remove the flywheel..just look with a flashlight if needed..
 
Yes, was charging before. I've recently added a switch panel and added a bow and stern light and manual bilge pump. It already had a fish finder that's always worked. Previously the fish finder was fused and wired to the ignition switch.
now the fish finder, navy lights, and bilge work from the new breaker/switch panel.
 
OK, one more thing to throw in the mix...

That little 32V 20amp fuse was blown on the wiring harness section that comes from the Rectifier back to the battery. Surely it couldn't be as simple as that. But maybe? Don't know why I didn't think to check that sooner. I've ordered 10 spares, and will see what happens...
 
check your additional wiring if it happens again....disconnect it to isolate...if you had the ignition switch out to disconnect the fish finder then eyeball that good to make sure you dont have a short there..or a loose connection flopping around...a 20 amp fuse dont blow for no reason....when you are testing it and looking around activate the bilge pump and make sure thats not when the fuse blew...if you have an auto bilge pump switch then activate it...it dont happen often but some fuses will heat up and not blow in a borderline situation and then blow later when a load is applied such as the starter......
 
So my son and I finally pulled the flywheel off to take a look at the stator. Unscrewed the stator coil, pulled it out and as I was doing so, it was apparent that 2 wires were broken. I fixed and thoroughly checked for any other damage to the wires and after being satisfied that they were now in good shape, completely reassembled, rechecked the point gaps, torqued down the flywheel, and reconnected the wires to the block with the rectifier. We also replaced that blown 20amp fuse that had obviously blown from the shorted stator wires.

Before starting, battery read 12.39 Volts

Upon starting, and at lowest possible idle, it immediately jumped to 12.7 Volts

Throttle halfway up, 12.9 Volts

Quick full throttle, 13.1 Volts

Will test better on the water tomorrow as I understand you don't want to run WOT in a barrel.

Thanks all for your suggestions! I learned a lot!

Leo
 
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