1991 Mercury 200hp V6 Overvoltage and Dropping Power

[Randy W.]

I'm having an issue with high voltage and motor dropping cylinders (power). Just had both switch boxes replaced (one tested bad) and the stator checked. Stator tested good. My mechanic indicated two cylinders were dropping out. BTW, compression at or about 110 on all 6. After the repair, it worked fine for about an hour, then voltmeter jumping from 14-16 volts. When jumping to 16 volts, the motor cuts out? I thought the ignition system and charging systems were separated on these older outboards? Thanks for anyone's thoughts. I hate to just keep throwing expensive ignition parts at it.

 

[sam am I]

They are....In fact, you should be able to totally disconnect all four yellow battery charge wires that run to the two rec/reg's from the stator and it should still start/run perfectly (less the tach).

The charge stator has a totally separate set of winding's (but within the same "charge winding" assembly) solely dedicated for powering the switch boxes.(The switch boxes contain their own internal AC > DC bridge rectifiers)

Moreover, the above mentioned charge stator is totally separate from yet another assembly called the "trigger"winding's that also wires to switch boxes.

 

[Randy W.]

Sam:
Thanks for the clarification. Any suggestion on where to start on the diagnosis of the dropping power issue? I'm thinking stator issues? Maybe regulator on the overcharge problem. Could a battery be related to these issues. I do have a service manual and parts book for this motor.

 

[Dukedog]

healthy battery is a must ta start off with... might be tha regulator.. possible stator or both.. you happen ta be one of tha "lucky" ones that have tha 40 amp stator (two yellow charge wires) with water cooled regulator.. its not tha best thing Merc came out with.. only around for 'bout 3 years till it was discarded.. your stator will only work with this type regulator and vice versa... both are very expensive pieces making right diagnostics imperative..OEM MERC manual for your motor "should" have tha procedures... after market, probably not... GL.

 

[sam am I]

A bit of a head scratcher that the two issues are even coinciding...........I've/others all have lost reg's on these blocks where the voltage was jumping up too high (tach may have been freaking too) and the motor still ran smooth. This to me sounds like a ground issue or stator issues because the two systems should remain mutually exclusive with the exception of a common factor of either, 1) ground or 2) the stator. Given that, I guess I'd start with a few fairly quick and easy tests .......

1) Check, recheck and tighten ALL the grounds lugs (and associated wiring as you go) on the block, try and run it again. If problem continues........

2) Disconnect the 4 yellow wires (tape/cap them off) and try and run it again.

My thought here, not only will this remove the reg's (should be a moot point) out of the picture for the moment, is that perhaps when the stator is getting hot/heating up (which it does) with normal batt charge load/s via the loads through the reg's, the stator's enamel could be cracked and expanding and a short to ground or across winding's is occurring in the winding's.

Thus, disconnecting the 4 yellow wires and running should allow the stator to run almost stone cold and perhaps help determine if it's heat related stator issue.

Vibration of course will still occur and it could still drop out and I guess at that point, I'd pop in a new stator.

 

[Dukedog]

forgot ta ask... motor carb or efi?..

 

[sam am I]

forgot ta ask... motor carb or efi?..

Good point Duke, that might switch it up a bit.as they could coincide.....A bad reg spiking the EFI unit? He could be dropping out due to fuel, that's for sure. If he pulls the reg's as a test, that would stop any EFI unit spiking. Hmmmm, this then presents an additional fork in the road if it runs well after wards.

If he's running EFI and it clears up with the old reg's disconnected, thinking I'd then probably lean towards 2- $40 amazon reg/rec's before the stator.

BTW, I don't think he running those water cooled reg's on that block, just the air cooled ones I believe.

 

[Dukedog]

unless he's made tha modification and is a '91 its tha single water cooled.....

 

[sam am I]

Oh crap, my manual cut off at and was showing 92 200 EFI with the air cooled, my mistake.

1991 200 carb has seperate rec and reg, both air cooled
1991 200 EFI single rec/reg water cooled

 

[Dukedog]

tha one (carb) diagram is wrong for most '89 up 150's and 200's... its for a 16 amp system... 9 and 16 amp are tha only ones that uses separate reg and rectifier....

 

[sam am I]

Not sure about that Duke, looks like they used a 40 amp stator with a 20 amp (16 amp) separated air cooled rec and reg. That's what they say anyway, who knows, the documentation could be wrong but, perhaps they were transitioning in that year, had made/ just developed the 40 amp stator's but, for the 91 200 carb'd motor's they just put on the old school separate 20 amp air cooled stuff? :noidea:

Seems tho running a 40 amp stator with 20 amp rec and reg could = smoke!! Air cooled, separate or not, hmmmm.

Maybe Randy will enlighten us.........

 

[Dukedog]

may be but have never seen it and dealt with "few V6 mercs" over tha years.. merc doesn't mix n match that stuff.. its either all 16 which will include a 16 amp stator, a separate rectifier, tha "notorious" 16 amp regulator, and "little" flywheel... tha separate rectifier goes away with any 40 amp.. tha air cooled 40 amp (dual reg/rec) stuff didn't come out till '92/'93... but it is a MERC soooooooooooo!

but think a 40 stator and 20 amp reg. jus won't je-ha very long.......

 

[sam am I]

Definitely agree.........I'm curious about that 2 yellow wire 40 amp stator's as opposed to the/my common 4 yellow wire twin 20 amp (40 total). When and why did they change over from 2 wire 40 amp to the 4 wire twin 20 amp?

Was the 2 wire 40 amp only used in EFI's in that 91 era? And there was also a 91 era 200 carb'd 2 wire 40 amp as well? I need enlightening.........

I bet it boiled down in the end for that merc had lots of trouble running 40 amps through one 4X6 (24 sq in) shunt type rec/reg, water cooled or not. They re-eng'd to split this greater power dissipation into a larger area of 2 4X4 (32 sq in) thus requiring two 20 amp winding's...BOOM, 4 wires were born.........just a guess tho and i digress, sry Randy

 

[Dukedog]

tha 40 amp came in '89 (not all '89's though) with tha single water cooled reg... they over heated right off tha bat mostly due to air pockets in coolin' system (exhaust divided plate).. they then added tha little hose from tha top of tha block to tha poppet cover ta help tha air pocket thing.. it did to a point but they were still prone ta over heat.. thats tha reason that little hose came about.. it did benefit tha air pocket issue so tha little hose became a permanent fixture on production motors.. they basically used tha public for R&D.. they dropped tha water cooled for tha present 2 reg. stuff in '92, maybe '93 best i remember... thats tha story as i know it but !!!!

and no, not jus efi's or 200's.. "most" all '90 up except tha 135 had tha 40.... even though some of tha 135's had it.

 

[sam am I]

I'll go with that story, works for me. Thx Duke, very interesting the evolution of some of this stuff........and yeah, my 92 has the two shunt rec/reg setup but, soon to be a more efficient series reg setup.....more later different thread.

Randy, read up...........lol. We have some possible help/answers up above but, different approaches that depends on what motor/system we've discussed down here.

 

[Randy W.]

Wow! Thanks for all the great information. For clarification, it is the carburetor version and has the two yellow wire regulator. Not identifying a rectifier anywhere? It appears like a "solo" water cooled regulator and I believe also that it is the 40 amp stator. I appreciate your ideas and discussion, Sam and Duke. I am electing to attempt to complete the repairs myself, due to my thin wallet! Parts for this era Mercury are very expensive as addressed above, so effective troubleshooting on my behalf would be great. Sam, per your suggestion, I've been reading a great deal. It is a "head scratcher" because I feel like the overcharging condition is related in some remote way to the power (dropping cylinders) condition. When the voltmeter on the dash peaked at 16+ volts, the motor cuts out. I realize they are separate systems and coils, yet a strange coincidence? Per the suggestions above, I have checked the grounds. Also, from the Clymer Mercury Manual, I ran the stator and trigger coil tests from the troubleshooting section. These are basic resistance tests and using a quality meter and a second one for validation, both the stator and trigger were well within specs. However, maybe they "breakdown" under a load from heat after an hour of boating? I like the idea of removing and insulating the yellow stator wires and checking it with the stator out of the equation. Anyway, I need a DVA adapter to continue my "fun". Any suggestions on that? I had one that I had "homemade" a few years back, and then I smoked it somehow. Thanks again for your thoughts!

 

[sam am I]

Beings it's a carb type motor then running/testing it without the yellow wires will just be that much more of a decisive test then, yes.

As Duke mentioned, you have the "all in one" 40 amp reg, it has an integral rectifier............

In addition to the load induced heating of enamel that's cracked and flaking the stator windings out theory, I'd also think/bet a flaking (intermittently shorting and opening, reg'ing and not...........jumping up to 16-17 then back down)) rec/reg could certainly be reflecting weird effects back into and creating odd saturation levels in the charge stator's magnetic couplings, perhaps creating strange effects in the entire assembly which sure might be effecting the adjacent switch box's charge winding's. Only one way to find out eh?

As for a DVA, I have a fluke 87-5 that is plenty fast enough to capture anything Merc rise time and hold it with a peak hold. There are probably several more meters, fluke and what-knots out there fast enough, not sure which model numbers tho. A DIY DVA build was posted here

 

[Randy W.]

Thanks Sam...going to do a little more troubleshooting with the DVA. Your assessments sure make sense given the behavior of my motor. Wondering now if both the stator and regulator are defective. The overvoltage occurs immediately upon firing up and the performance problem occurs an hour later.

 

[Randy W.]

Update: I took some DVA readings on the left and right yellow stator wires (still connected to the regulator). I am using the CDI troubleshooting guide. The left and right readings were 17.26 and 17.30 respectively measuring each terminal to ground. They indicate each should be wthin 1.5 volts of each other. Then I measured from each yellow to red and got readings of .73 and .71 using the ESI DVA adapter and a decent Radio Shack digital meter on auto ranging and then on manual modes. The stator readings should be much higher? Readings were taken at approx. 1000 rpm. Still haven't been to lake to test with yellow stator wires disconnected.

 

[sam am I]

The stator readings should be much higher? Readings were taken at approx. 1000 rpm.

You're measuring those 17VAC's from ground? The Block? Hmmmm, I'm not sure about the 2 yellow wire stator's but, I know my 4 yellow wire stator wires are all isolated from ground. As a test on the four wire units, Merc, in fact has a current test measurement to assure there is NO current path on AC side (yellow wires) to ground.

From what I read about your setup, and which is similar to mine (minus just an extra winding), you should see "16VAC" ACROSS the two yellow wires, NOT to ground on either yellow wire.

Maybe your stator's change winding is shorted to ground? I'm not sure though but, I wouldn't think Merc ground referenced (center tapped) the AC side of your stator's charge winding's.......If the charge winding is suppose to be isolated, you disconnect the yellow wire/s and ohm them to ground.........

See section "40 Amp Alternator (stator) with Large Regulator"