Problem with stator, voltage reg, or other... I am lost

[codyclyatt]

Hey everyone, I am stumped, of course I don't know what I am doing either lol. Here is the problem.... I have a 1995 mercury 90hp 2 stroke, model number 1090412RD. I am yet to run the boat on a lake since I bought it but noticed how the battery was not charging when running it on a hose at the house(12.5 volts no change while running). I do at least know that the voltage regulator is shot because it has a burn hole in the bottom of the epoxy and you can see the fried diodes inside. I am worried that the stator might be bad also but am unsure and do not want to order something that I do not need. While the boat was running I checked the 2 yellow wires that goes into the voltage reg and see less than 1 volt per wire. I did read online somewhere to check the ohms on the red wire that goes to the switch box between ground, I am coming up with 120+/- ohms which leads me to think the stator is bad. Any help would be appreciated, what else should I test?

[straffordengineer]

I'm not sure I am following you on your voltage check of the yellow wires. You cannot check the voltage independently; the stator is ungrounded therefore you need to check the voltage between the two yellow wires (put one test lead on one yellow wire and the other test lead on the second yellow wire). Voltage will be AC so make sure your meter is set to AC.

Are the bullet connectors on the yellow wires burnt? There should be a total of 4 bullet connectors. Two connectors are near the voltage regulator and 2 connectors are near the stator.

Check the voltage between the 2 yellow wires and report back.

[EuropeanAM]

Good information above.

IF the stator tests good (producing AC voltage between the two yellow wires, no burnt/melted/discolored bobbins when visually inspected, and no continuity to GROUND on either yellow wire):

-REPLACE VOLTAGE REGULATOR with an OEM (Mercury) Unit ONLY.

-REPLACE ANY DAMAGED BULLET CONNECTORS (browned/blackened/melted)

-LOAD TEST battery to confirm it's GOOD

-CLEAN battery terminal connections, ensure ENGINE cable installed FIRST, remaining lugs Largest to Smallest, and finish off connections with a Stainless Locknut (do NOT use wing-nuts).

[codyclyatt]

Ok I tested the AC output between the 2 yellow leads that go to the voltage regulator, all the way idled down it was 16 volt, when I throttled up a little the voltage increased

[EuropeanAM]

Good information above.

IF the stator tests good (producing AC voltage between the two yellow wires, no burnt/melted/discolored bobbins when visually inspected, and no continuity to GROUND on either yellow wire):

-REPLACE VOLTAGE REGULATOR with an OEM (Mercury) Unit ONLY.

-REPLACE ANY DAMAGED BULLET CONNECTORS (browned/blackened/melted)

-LOAD TEST battery to confirm it's GOOD

-CLEAN battery terminal connections, ensure ENGINE cable installed FIRST, remaining lugs Largest to Smallest, and finish off connections with a Stainless Locknut (do NOT use wing-nuts).

Proceed with the remaining recommendations in the above quote.

[codyclyatt]

Thanks for the help guys... I am guessing that the 16 volts at idle is where it should be? Also when I hook up the new voltage regulator does it matter which way the yellow wires connect? There are 2 identical ones on the regulator and motor. Again, thanks a bunch for the help

[straffordengineer]

It doesn't matter which way the yellow wires connect. It is alternating current (AC) so the connections are bi-directional.

[Ba$$n]

Voltage should not exceed 14.5 or it can damage your battery and electrical components on the engine.

[straffordengineer]

Voltage should not exceed 14.5 or it can damage your battery and electrical components on the engine.

14.5 is the max DC voltage out of the voltage regulator not the AC voltage on the yellow wires. 16 Volts AC on the yellow wires at idle is about right.

[EuropeanAM]

14.5 is the max DC voltage out of the voltage regulator not the AC voltage on the yellow wires. 16 Volts AC on the yellow wires at idle is about right.

Actually, 14.6 VDC from the regulator is the "max". You have good output from the stator... INSPECT as suggested above, and proceed with the necessary repairs as described.

Yellow stator leads aren't polarity sensitive, as strafforengineer mentioned, it's alternating current, so it doesn't really matter which yellow lead is connected to which regulator input wire (as long as yellow is matched to yellow, of course).