1970's Merc 500, Questions about Stator performance or lack of...

[Roadblock]

I have a 1970's Merc 500. Engine is running pretty good right now but I'm about to rebuild the carbs and I've repaired some wires that look less then um, safe!

I have a question about the stator.

So if this part is working properly, should the battery loose power as the engine runs? Is there anything else inline with the Stator that can cause it to not preform as expected? I have a BRAND new class 27 battery that is dedicated to starting and running my Merc 500. I've noticed that I loose voltage when running the motor. I was under the impression a stator runs exactly the way a automobile alternator runs.

For example, I went fishing the other day and I maybe had um 20 minutes of run time and the battery was at 92% when I got home.

Week or so ago I took it out on a river run, I ran 6 gallons of fuel, total run time was roughly an hour and my battery was around 85% after that.

This is not normal right? Are there tests I can do to see if everything is running right? If I didn't recharge my battery after getting home, it would eventually be dead.

Again this battery is dedicated to starting and running the motor. Motor starts right up and runs fine btw.

 

[Nathan Bond]

Not familiar with that model, but typically charging is done by the rectifier. Check voltage at the battery when the boat is running. If the rectifier is working you should be getting up to 14.5 volts or so at the battery. The battery really shouldn't be draining as the engine runs, once the boat is started. The stator pretty much provides all the voltage the boat needs after that.

 

[Roadblock]

Yes but what I mean is that doesn't the Stator create power that the engines uses to recharge or maintain the charge on the motor? It may get it by way of the rectifier but it comes from the stator correct? It's basically the boats alternator as I understand it.

OK so that said, if either part was not working as it should, would the engine run? I mean my boat runs fine, I just loose power off the battery. Even if the rectifier was not working correctly, if the boats stator was putting out a enough power to run the motor, the battery shouldn't go dead should it?

I don't know why I didn't think to check power at the battery! Same thing you do on a car....

 

[enginepower]

Well, a stator has several functions on most outboards. Several poles are used to charge your battery. 2 other poles are the high and low rpm indicators for the controlling module. If your battery keeps going down as you run down the river and you don't have heavy loads on it (2 kicker 10" subs and a 500W amp for instance lol) the battery should keep a fairly high state of charge. Note: the depending on size of stator, you will get on average for most engines about 15 amps of charge out of it. I think some have large capacities and can produce much more.