(Testing Tachometer With Water Cooled Regulator/Rectifier)
(J. Reeves)

A quick check is to simply plug in a another new tachometer as a piece of test equipment. If the new tach works properly and the old tach didn't, obviously the old tach is faulty.... but usually boaters don't carry around a spare tach (see below).

A faulty rectifier wouldn't damage the tachometer, the tachometer simply wouldn't work. This is due to the fact that the tachometer operates off of the charging system and the rectifier converts AC voltage to DC voltage, enabling the charging system. A faulty rectifier disables the charging system, and the tachometer simply doesn't register.

However.... those water cooled regulator/rectifiers that are used on the 35 ampere charging systems (and some others) bring into play a different type problem, and as you've probably found out, they are really a pain to troubleshoot via the proper procedure. There's an easier way.

The tachometer sending/receiving setup operates off of the gray wire at the tachometer. That same gray wire exists at the engine wiring harness which is connected to the engine electrical terminal strip. You'll see that there is a gray wire leading from the regulator/rectifier to that terminal strip, and that there is another gray wire attached to it. That other gray wire is the wire leading to the tachometer which is the one you're looking for.

NOTE: For the later models that DO NOT incorporate a wiring terminal strip, splicing into the "Yellow Wire" mentioned will be necessary.

Normally the Gray wire leading from the tachometer is attached at the terminal strip to another Gray wire which leads from the water cooled voltage regulator/rectifier...... remove the gray wire that leads to the tachometer. Now, find the two (2) yellow wires leading from the stator to that terminal strip. Hopefully one of them is either yellow/gray or is connected to a yellow/gray wire at the terminal strip. If so, connect the gray wire you removed previously to that yellow/gray terminal. Start the engine and check the tachometers operation, and if the tachometer operates as it should, then the regulator/rectifier is faulty and will require replacing. If the tachometer is still faulty, replace the tachometer.

If neither of the yellow wires from the stator is yellow/gray, and neither is attached to a yellow/gray wire, then attach that gray tachometer wire to either yellow stator wire, then the other yellow wire, checking the tachometer operation on both connections.

I've found this method to be a quick and efficient way of finding out which component is faulty.... the tachometer or the regulator/rectifier. It sounds drawn out but really only takes a very short time to run through. If the water cooled regulator/rectifier proves to be faulty, don't put off replacing it as they have been known to catch on fire with disastrous consequences.

I actually am not too concerned about the tach. I just didn't want overcharging to hurt my battery and electronics. I think 17 volts is too high. I couldn't even find where the regulator was on the motor.

I assume your powerpack is located in the same area as per past years, that is to the rear of the flywheel.

The voltage regulator/rectifier would be located beneath that powerpack.

Whether you're concerned about the tachometer or not is none of my concern... BUT... in this case it is used as "test equipment" to determine the condition of the regulator/rectifier. One of my comments states........

"If the water cooled regulator/rectifier proves to be faulty, don't put off replacing it as they have been known to catch on fire with disastrous consequences." I am dead serious about that... many a boat owner has turned around to see his hood burning off the engine!

Thanks, I am not sure if using the tach will help me any. It starts out fine then after I shut it off for a while and then restart, that is when it starts acting up. It may or may not jump around so I don't know how to test it. My depth finder displays voltage and that is how I saw the fluctuation. That too doesn't always read fluctuate. Maybe my regulator is starting to go bad and when I park it for a while in the sun and warm engine it heats up giving me trouble. Thanks for the help. Is this what I need? 0585195 EVINRUDE/JOHNSON RECT/RGLTR AY,3/10

Well after I ordered some parts and looking at them, I figured out that I have an unregulated system with just a rectifier(explains the high voltage) . I changed that ,but haven't tried it. The boats.net showed a voltage regulator/rectifier assembly also, so I ordered that as well at the time. I see I have a plate where the regulator assembly must mount if it was installed. It looks like I can remove the plate and install the unit. Can I just wire it in, there are 5 wires yellow, yellowgrey, grey, red, and purple. My rectifier has 3, can I just unhook the 3 from the rectifier and add the purple and grey in the spots marked on the terminal strip. Do I have to remove any jumpers on the strip? I can't just return the regulator/rectifier assembly since it is an electronic item so I might as well try to use it. Thank for any help

20A fuse blows while motor still runs

This thread is real close to my problem. I have a 2003 40hp with remote control.I have the tach with warning system. Sometimes the Tach works, sometimes not. Put the boat up at the end of the day. Next time I went to use it- no start-no crank- battery 12.6. Found the fuse was blown. replaced. when turn key to "on" I heard the fuse blow. I could not find where the short is. I cleaned all the connections at the terminal strip. Short "gone"-starts runs. Check battery voltage getting alt current no tach. shut down and start getting 14.6 DC- I think i had tach then. next run out on the Bay- I get momentary warning horn, temp,then oil, then just horn, then nothing, all in about 3 seconds, tach out again. shut down fuse blown. So I definitely have an intermittent short. Can the warning system tach short the grey high voltage AC back to the terminal strip to pop the fuse?
My power pack (independent of reg/rect) runs the motor with the fuse blown. That is why I can't tell what is the culprit. Can the regulator/rectifier act up intermittently, or is it either good or permanently bad? Can the Powerpack short to ground and blow fuse but still run the motor? When the oil warning came on I noticed it would only happen when the ride was smooth plowing. On plane banging the 16ft skiff in chop, it did not happen. Plenty of oil, so can the oil float sensor short to ground, then when rapidly swinging up & down (banging off chop) clear the short? If I replace the reg/rec, can a bad warning cluster/tach ruin the new one? Or a bad powerpack ruin a new one? Every time I turn the key & get no tach, turning the key off, then on & start again may or may not restore tach- intermittent/inconsistent- I'm down to my last fistfull of hair, the rest I've torn out in frustration!
Upon further examination of the wiring schematic I saw that the VRO pump has Positive on purple wire AND grey AC pulse on grey. Unplugging the MWS harness at the tach does not disconnect the VRO points of introduction to the Main wiring harness. I wanted to unplug it but the connector was not visible. I removed the starter for access and discovered that the rear of the VRO has a circuit board encase in a gel. The fuel/oil pump castings were warped and had leaked fuel onto the gel, exposing the solder joints. The VRO is positioned such that one of the solder joints is directly in front of a carb bolt (engine ground). The gel had swollen and pushed the solder joint closer to the bolt. The gel was weak and vibration caused intermittant shorting of the grey pulse AC AND the purple positive to ground & pop the fuse. The engine would continue to run, just no Tach. I hope this helps the next person with mystery fuse blow.