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Author Topic:   1994 Mercury 200 Charging, Starting Problems
Mister S posted 07-31-2006 08:38 AM ET (US)   Profile for Mister S  
I'm having electrical problems with my 1994 Mercury 200 Offshore. Early this season I replaced both regulators and rectifiers with after market ones since one was burned and my tachometer not working. It had run this way for months. I also installed two Group-24 AGM batteries. Everything worked great for a couple months. Suddenly my voltmeter and battery indication read over 16.5- volts when running. Batteries at 13.4-volts [under some condition]. Are the aftermarket rectifiers suspect? Did something else cause the failure? I hate to waste over $175 for new ones if they are going to fail. Can I test the stator with bad rectifiers?

I also have a long standing starting [problem] where it can take several tries to get the starter to engage. Has plenty of cranking power when it goes, just won't engage like it's not getting enough voltage at first. I am thinking the key switch may be bad. I'll have to do more checking. Fired right up when I watched with the cover off. Not sure starter is kicking in.

Dan S.

jimh posted 08-01-2006 08:25 PM ET (US)     Profile for jimh  Send Email to jimh     
Check your primary battery distribution wiring for loose connections.
jimh posted 08-01-2006 08:36 PM ET (US)     Profile for jimh  Send Email to jimh     
There are many devices in the engine starting circuit which can lead to failure to crank. Check all of these:

--battery distribution under cowling to fused +12 volts to remote start switch
--wiring harness from engine to remote start switch
--remote start switch
--neutral safety switch
--starter motor

There are many connections, terminal, wiring harness, and other electrical devices in the circuit which can cause an open circuit. Carefully check the continuity of all of these devices. I recommend a carefully disassembly and cleaning of all connections and terminals.

To perform this troubleshooting you need a good voltmeter and a thorough understanding of simple DC electrical circuits. If armed with these, it will be a simple matter to locate the problem, unless it is one of those frustratingly intermittent gremlins that can plague you for weeks!

Mister S posted 08-02-2006 08:35 AM ET (US)     Profile for Mister S    
Thanks Jim, Did some testing and snooping around last night, didn't come up w/ much. I'm going to pull the battery switch apart and clean connections and continue to the motor. The rectifiers don't look damaged/ burnt as one did in the past (I know that doesn't mean much). Volt meter shows 13.2 at rest, up to 17v high speed.
Starter finally acted up w/ cowling off. Doesn't always kick out far enough to engage. Will probably pull it out and inspect / clean it. Does anyone rebuild these? or replace.

Dan S.

jimh posted 08-02-2006 09:33 AM ET (US)     Profile for jimh  Send Email to jimh     
I am suspicious of the accuracy of your voltmeter. Most batteries will not show 13.2-volts unless they just came off a charger. A more typical resting voltage for a fully charged battery will be around 12.8 volts.
Mister S posted 08-04-2006 09:11 AM ET (US)     Profile for Mister S    
The 13.2 is after running, even for a minute or so at idle. The batterys are AGM's and they hold charge.
Even if the readings are a bit off - how much is too much charging voltage? Are the regulator / rectifiers the only cause. What causes them to fail, if they did?
rtk posted 08-04-2006 10:46 AM ET (US)     Profile for rtk  Send Email to rtk     
Check with the manufacturer of your AGM battery regarding preferred charging voltage. Most I have seen recommend that the charging voltage not exceed around 14.5 or so volts.

17 volts is way too high. Low 14 volt range is more typical.

My 1997 Mercury 225 and my 2003 Mercury 250 EFI charge at 14.2 volts when running.

If you have an owner's manual for the engine it should give you the voltage specification that the engine charging system should operate at.

A factory service manual would help in troubleshooting the cause of the overcharge.


andygere posted 08-04-2006 11:21 AM ET (US)     Profile for andygere  Send Email to andygere     
It sounds like the starter problem is a worn out bendix unit. If the motor is good, you can remove the bendix and bolt on a new one. I had the same problem with my 1989 Mercury 200.
Mister S posted 08-08-2006 03:04 PM ET (US)     Profile for Mister S    
Seems that battery selection also makes a difference of a full volt. (never seemed like much before) That tells me I also have a bad connection. At idle charging seems O.K., above 3000 rpm goes too high. Testing rectifiers and stator next. Thanks for replies.


sosmerc posted 08-15-2006 12:34 AM ET (US)     Profile for sosmerc  Send Email to sosmerc     
The alternator-driven 40 amp Merc charging system DOES NOT work properly with AGM or GEL batteries. If you run much at high speed you are going to fry your regulators and melt your stator. You could also burn up other electrical components as the voltage starts to climb above 15 volts.
Merc recommends conventional flooded starting batteries for this system. Believe me, I have "been there, done that" on this one.
Mister S posted 08-16-2006 09:31 AM ET (US)     Profile for Mister S    
sosmerc, What does using the AGM's do to the system? At high speed it's charging up to 17.5v. I was thinking of putting in a lead acid battery to compare readings. Don't want to replace rectifiers at $150 ea. w/o knowing. Saw your post about CDI rectifiers, are they O.K.? I've done some of the testing outlined in my manual but most of it is geared at finding a low voltage problem. Probably headed for the shop. Thanks for the replies.


Mister S posted 08-25-2006 01:12 PM ET (US)     Profile for Mister S    
Update : Replaced stator (high speed coil n.g.) both regulators (one was bad) and replaced AGM batteries w/ conventional lead / acid. SOSMerc hit it right on the head. This was not cheap - stator and regulators $700+. 2 new batteries another $200. Thanks for input and suggestions, anyone want to buy a couple new AGM's?

Dan S.

phatwhaler posted 08-25-2006 01:26 PM ET (US)     Profile for phatwhaler  Send Email to phatwhaler     
As the owner of V6 Merc with the 40 amp charging system I just want to say thanks for actually coming back on the forum and giving us an update.

pw out.

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