92' Merc Black Max 135 Stator Trouble
635
14
Looking for some experienced help with this one.
Backstory:
Recently the motor has been bogging under acceleration with a good load. Eventually the RPMs rise and the boat gets on plane but nothing like it used to. I pulled the flywheel to look at the stator prior to reading it with a meter but DVA voltage checks on the coils are high and unstable. Also, a voltage check of what the regulators are putting out shows a constant high output of over 17VDC which I know is not good.
Attached is a quick pic of the stator and it looks burnt to me.
What has changed recently? Well, I've been running my kicker (Merc 9.9 4S) a lot fishing. I have both motors connected to one battery without a switch. Just directly connected. I don't run them at the same time. Only for a few seconds when I 'm moving from one to the other.
Is having them both connected causing a cross charging condition where the kicker's charging circuit is harming the main motor? I've had plenty of people tell me that they run both motors on one battery with no switch and no trouble.
Want to get this figured out before I put the new stator in ($350). Figured I'd go ahead and replace the switchboxes and V-regs at the same time just to be sure about this ignition issue.
Thanks in advance for the help.
![Automotive tire Motor vehicle Automotive design Bicycle part Rim]()
Backstory:
Recently the motor has been bogging under acceleration with a good load. Eventually the RPMs rise and the boat gets on plane but nothing like it used to. I pulled the flywheel to look at the stator prior to reading it with a meter but DVA voltage checks on the coils are high and unstable. Also, a voltage check of what the regulators are putting out shows a constant high output of over 17VDC which I know is not good.
Attached is a quick pic of the stator and it looks burnt to me.
What has changed recently? Well, I've been running my kicker (Merc 9.9 4S) a lot fishing. I have both motors connected to one battery without a switch. Just directly connected. I don't run them at the same time. Only for a few seconds when I 'm moving from one to the other.
Is having them both connected causing a cross charging condition where the kicker's charging circuit is harming the main motor? I've had plenty of people tell me that they run both motors on one battery with no switch and no trouble.
Want to get this figured out before I put the new stator in ($350). Figured I'd go ahead and replace the switchboxes and V-regs at the same time just to be sure about this ignition issue.
Thanks in advance for the help.
1 - 15 of 15 Posts
77 lookies and nothing?
No matter. I ordered a new stator, 2 switchboxes and 2 voltage regulators. And a battery switch. Sometimes you just have to throw a big bag of money at the problem.
No matter. I ordered a new stator, 2 switchboxes and 2 voltage regulators. And a battery switch. Sometimes you just have to throw a big bag of money at the problem.
Is "missing" a lot?
I guess you could say that. Just sounds really, really rough as power is applied. If applied slowly it sounds its rough, just doesn't like it at all but slowly comes around to a slowly rising RPM until it gets to the amount of throttle applied. If full power is applied quickly it bogs and thinks about it for a bit then slowly comes up to speed. Half the stator is burnt black and one of the Service Manual meter tests indicates an open circuit that is supposed to be .45ohms. That long reef run a couple weeks ago really made it worse and I had to roll up my sleeves and see what's up. Fuel system is tip top.
Doesn't scream electrical to me. Have you looked at fuel delivery?
Nevermind you said fuel is good.
Nevermind you said fuel is good.
The charge output on the main motor is most likely a higher amperage than the 9.9,i would think it would suffer ill effects and not the 135 hp.
Yes. The main has a 40 amp stator on it to charge 2 batteries simultaneously (overkill for my application). I was thinking the same way as you that the 6 amp stator on the 9.9 kicker would lose that battle if they were both running at the same time for long. I know my main stator is fried and it either took itself out from heat produced by the engine over 30 years of use or, it was taken out by a bad V-reg. or switchbox. Rather than chase my tail replacing one part at a time I decided to just replace all of it at once. Parts arrive today so we'll see.
That is a long run you just did to the Reef, that would probably make it show it's age in this hot weather.
that long on a merury stator, you did very well.
when i was a mechanic you would not believe all the bad stators merc had, and if you went to a great shop they alot of times could get it covered.
if i recall correctly most merc stators from the 90s and before have went threw atleast 10 diffrent upgrades.
Sent from my SM-N986U using Michigan Sportsman mobile app
when i was a mechanic you would not believe all the bad stators merc had, and if you went to a great shop they alot of times could get it covered.
if i recall correctly most merc stators from the 90s and before have went threw atleast 10 diffrent upgrades.
Sent from my SM-N986U using Michigan Sportsman mobile app
Now that is interesting. I had heard that Merc stators from that period were sketchy but not that bad. Wow. I guess I have been lucky and I don't know if this one was the original but someone had written orientation notes on top like "Front" and "Aft" in red sharpie. That tells me it was at least removed at one time and put back on.
I really hope this CDI replacement is reliable since I plan on doing more runs to the reef. Besides the reef I'm often out 10 miles or so and would not relish a trip back in on the kicker on a rough day.
I really hope this CDI replacement is reliable since I plan on doing more runs to the reef. Besides the reef I'm often out 10 miles or so and would not relish a trip back in on the kicker on a rough day.
I for one have seen more Mercury triggers fail (blistered and cracked) than stators.Parts from CDI are in many ways built better than oem. Some where in the charge circuit there must be a diode that will prevent cross charging feed back allowing a 2 motor setup on one battery...
Another thing to remember is a bad rectifier regulator will overheat your stator...
Well, all the new parts are installed and checking voltages in the driveway on muffs everything seems nominal. Spark gap test on all cylinders shows a nice fat, blue spark which is a huge improvement. Charging system that was (according to the service manual) in a Constant High Output mode is now down to about 14.8 - 15VDC and that is much better. Taking it to a local lake for some WOT tests with fingers crossed.
Man, it runs like a champ now. So much more power throughout the entire range of the throttle. No more peaky power band and smooth as silk. Its like a new motor. Problem solved and it was worth every penny.
Glad for the follow up.!
1 - 15 of 15 Posts
