1968 Mercury 650SS Not Charging

TMAD

Cadet
Joined
Aug 14, 2012
Messages
6
Hello All,
Like the title says I have a 1968 Mercury 650SS outboard with a thunderbolt ignition system. Engine serial number is 2313454.
Here is the history. I bought the boat three months ago and finally finished working on the boat and can concentrate on the engine now. I have cleaned the carbs with my ultrasonic cleaner and installed new carb kits. The plugs were changed and the distributor was cleaned. When went to start the engine it started quite fast and idled very nice with just minor adjustments to the carbs. Here is where things start to go sideways. I tested the voltage across the battery and I was only getting 12.40 VDC. I checked the rectifier with my fluke meter and found that it was no longer working so I replaced it with a GBPC2510. Once the modifications were done I connected the alternator stator wires (two yellow) to the rectifier and did not attach the positive to the electrical system yet. I started the engine and found the new rectifier was producing 15.8 VDC, high but not too high. I connected the DC side to the electrical system and moved on to time the engine before testing the voltage again. Bad call on my part but we will get to that. I wanted to do a timing check and found the marks on the fly wheel and put some white out on the marks, all standard stuff for working on engines. When I had it idling I found that my marks were nowhere to be found. After stopping the engine I recognized a pant chip from the strobe light and it was exactly 180 degrees from my marks. Someone had taken the flywheel off and put it back on backwards. I turned it around and tested the timing again. It required only a little timing adjustment in the full throttle position and I was very pleased with how things were progressing. So now I get around to testing the voltage again and find that I am still only getting 12.40 VDC on the battery. I pull the ignition system off the rectifier and the rectifier is only producing around 12.34 VDC now. I left the stator leads connected the rectifier and tested the AC voltage from the stator and I was only getting a reading of 10.5 VAC well this does not seem right. I would expect it to be a lot higher but I do not know the value for this stator at idle. With the engine off and the stator leads disconnected i am getting 1.2 ohms across the leads.
So here are my questions to you experts.
1. What is the ACV of the stator at idle suppose to be?
2. What is the resistance of the stator suppose to be?
3. What is the maximum current output of the original rectifier? The manual says 6-8 amps and the new rectifier is good up to 25 amps.
4. Is my flywheel orientation changing things that i am not paying attention to?
That is all for now and I look forward to everyone?s thoughts of this situation.
Thanks
Tim
 
M

Maxz695

Guest
Re: 1968 Mercury 650SS Not Charging

This is a repost but again the flywheel position will not be the fault of the rectifier not putting out it,s proper voltage. Do you have a tach hooked up to the rectifier? Grey wire ? If the tach is bad it may be affecting the rectifier output. I would temporarily disconnect the tachometer wire from the rectifier and retest it. If the tach is working properly try swaping the yellow wires and retest it. Posible causes are bad windings in the stator, the rectifier was shorted again or bad wiring in the harness somewhere
 

TMAD

Cadet
Joined
Aug 14, 2012
Messages
6
Re: 1968 Mercury 650SS Not Charging

Yes this is a repost because I found out that I didn't tag any words and don't know how to go back and do it. Shoot I don't even know how to find my own post once my email tells me that there is a response. I had a tack connected but through the brown wire on the switch box but have since disconnected it because it was not working. I agree that the changing the place of the fly wheel shouldn’t affect anything but sometimes there are strange little things that only people that have been working on these things for a while know.
I will try to get the RPMs up and see if things get a little better but it would be nice to get a working tack as well so I can make sure all the timings and carb adjustments are correct before guessing at the settings. By tack is only a two wire tack “GRN” and “S” so who knows where this came from or how to hook it up to this system?
I won’t hold my breath for anymore for specific answers to my question but i do hope some that know about this engine can help me out.
Thanks for the advice and I will keep you posted.
TMAD
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: 1968 Mercury 650SS Not Charging

Even the newer stators do not charge much at all at an idle.

Charging voltage needs to be check nearer 1800 - 2000 RPM.

UN-loaded the voltage can seem quite high as the UN-regulated voltage is free to climb, that is, the battery is actually the regulating factory, holding the voltage to whatever the battery will allow. This is why it is critical to use only a lead-acid battery and to regularly check water levels.
 
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