1999 Mercury 200 XL Carb- Charging issue

[medfire]

Hello all! Long time lurker, first time posting.

I have a 1999 Mercury 200 XL Saltwater Carb 2s- Serial #- OG803976

I have been having some trouble lately with the electrical system and wanted some advice.

About a month ago, I had an issue where the starter would just spin but would not engage the flywheel, I changed the starter solenoid and the starter and it fixed that issue. Soon after I was on the water one day and after several starts and stops and running and idling all day while using the stereo and various other electronics, we stopped at a marina for about 30 minutes and the motor would not start, it would turn over but would not start until I finally wore both batteries down although it still cranked it would not start or run. Towed it back and before I did anything else to diagnose the issue I charged both batteries overnight. Came back the next morning and the boat fired right up no issue.

Was working on the boat yesterday and was running it on the muffs and noticed the temp gauge was dead, diagnosed that to a loose ground in the head that holds the temp sensor in and just went ahead and replaced that as well while I had it off. Works fine.

I charged both (brand new) batteries before we left for the ramp and boat cranked right up and ran beautifully, idle, mid range, WOT, up on plane all good. I checked my analog volt meter on the dash was reading right at 12 no matter what RPM I was at, checked it on my Garmin and was reading at 12.5 while idling or mid range RPM and 11.9 WOT. I had the stereo on for the kids and my GPS running besides the motor. I usually flip my bilge on when I am running for a few seconds to check for water (usually a little, but I have OCD about it). When I pushed the bilge switch the GPS and the Stereo completely shut off. I killed the bilge, turned everything back on and it was fine. The motor never even blipped. Went to dinner, shut both batteries off, came back fired right up and headed out (Stereo and GPS again, no problem) it was dark so i put the nav lights on and my LED strips under the gunwales, still fine. Flipped on my rear spreaders for a second and bam, everything electronic went out again, motor still running great. turned the spreaders off, fired everything back up and ran great.

Haven't had a chance to check the batteries yet but will tomorrow morning, I am guessing that they will be very drained.

So after my life story, my question is, the theory among the firefighters round table is either the stator or the rectifier. I do not have a flywheel puller but can get one and probably take it somewhere to be checked but I was hoping for some insight or experience to determine what this could be? Of course the Stator is close to $600 for this motor (all the other Mercs are $169!). I know I could take it to a Merc repair shop in town but I am pretty mechanically inclined and like to do things myself if I can but if I have to I will take it in.

My theory is if it was the stator, it would (or should) affect the running of the motor, like no power to the coils, missing, falling on its face etc, but the motor runs perfectly, I REALLY stay on top of the maintenance and the motor is like new. However if the rectifier is not working it is just not putting the voltage back into the batteries and everything is running off the ever depleting batteries? Just a theory, I am sure someone out there knows WAY more than me.

Thanks for reading and any help would be appreciated.

 

[Chris1956]

OK, a couple of things. The ignition runs off the stator, and is not connected to the charging system. However, the engine must spin fast enough when starting to have good spark. That is likely why she wouldn't start with drained batteries.

You have dual voltage regulators, likely 20A each. Usually the voltage regulators break, before the stator. Check them for burn marks on the circuit boards. Of course the definitive test is to check for stator voltage at the voltage regulators. This voltage would be AC. so disconnect all yellow wires at the VRs and test them for AC voltage. If you have voltage, replace the voltage regulators. CDI makes some cheaper than OEM models. If no voltage, the stator is likely bad.

Replacing the VRs is a nuts and bolts job. Likely 15 min. Also, I recommend you go thru the boat and clean up the electrical system, as it sounds like you have multiple electrical connection issues.

 

[medfire]

Chris, thank you so much for replying and helping me with my issue. I agree about the issue at the dock, my guess is that there were not enough RPM at the dock to fire the motor. It started immediately after I charged the batts at home.

After my post, and when I got home, I looked at the wiring coming from the stator to the VR's. The top VR yellow wires were burned at the connections and the heat shrink around the bullet connectors was melted and burned. Actually one of the yellow wires was melted to one of the red wires but not through to the core.

I wish I saw your reply earlier so I could have checked the output of the Stator before I removed the VR's. I already ordered them and they will be here tomorrow. I really hope it was those and not the Stator but we will see.

I am pretty OCD about maintenance all the way around the boat, I have replaced or rewired a good portion of the systems over time. I have had a few problems with grounds backing out or old hidden wires wearing out but I am getting to them as fast as I can. I believe the reason the GPS/Stereo shut down upon activating the spreader lights and the bilge was that there was not enough voltage to run those things at the same time. The bilge pump and the non-LED spreader lights take a lot of juice, so hopefully that is the issue.

I really appreciate the help and will update the post after I put the new VR's in on Wednesday.

Thanks again,

 

[JDusza]

Given the engine runs, it sounds like the stator is good. The stator generates AC so this has to be changed to DC with rectifiers within the voltage regulator. If engine runs and batteries are not charging, sounds like rectifier/regulator problems.
Test battery voltage while running. It should be marginally greater than 13 v.
J

 

[Chris1956]

J- you do realize that the coils that run the ign are different that the ones that feed the VRs, right?

 

[medfire]

Thanks again for your feedback and help.

I installed the new VR's yesterday and all seemed to work perfectly. I was unsure what to do with the gray wire on the bottom VR, the previous one which was not burned that I could see had the gray wire sealed off with marine epoxy (I am guessing to keep water and debris out of it) but I connected the top one as before and resealed the bottom one.

I got great charging readings on both analog and digital voltage meters and the voltage increased with the higher RPM as expected. Hopefully this was the issue and the Stator seems to be working fine.

Once again appreciate all the help. I will be posting another issue I am having with a tilt gauge/sensor today.

 

[Chris1956]

Both voltage regulators are identical and as such, have the grey wire that would connect to the tachometer. However, you only need one of them, so the other one is sealed, usually with a rubber plug.