Mercury 50ELPT BF charging issue 50hp 4-stroke

[asdasc]

I have a Harris Pontoon with a Merc 50hp engine and it has stopped charging the battery. I got it new on the boat about 5 years ago, but it looks like a 2012 engine. Is that odd? Anyway, if I put a fresh battery in, it runs and starts fine until the battery starts getting weak, and then it starts to idle rough. I thought it should be able to run without the battery completely?

I replaced the rectifier/regulator, and no help. I based this on using a voltmeter on the battery at 2000rpm, it only reads 12v. I am assuming that it means the stator is the next part to replace? I have read some things about having an alternator, but I don't see one mounted anywhere, unless it's integrated into the starter? Assuming I need to replace the stator, how big a job is it to pull the flywheel? I have done it a few times on 1950's and 1960's smaller outboards, but never anything this big or new.


Thanks,
Steve

 

[asdasc]

Is there anything else that it could be, or should I just order the Stator and take this thing apart? From the parts guide, it looks like the part number is 878143T05, which I believe is the 16A version. Is there a way to test this thing without tearing the flywheel off?

 

[asdasc]

Bump...

 

[Texasmark]

The regulator/rectifier is fed by the two yellow wires (on Mercury's) from the stator. Their resistance is almost zero ohms between the two plug in terminals and infinity to ground (isolated). AC power is fed to the rectifier half of the assembly and then regulated by the other half. Output is unreliable below 1k rpm but the Mercury service manual has an amperage per rpm chart. Max output is 16 amperes for the Red stator (just look up under the flywheel and you can see the color) and max voltage, at WOT and a full battery is 14.5v.

If you are running your engine at an rpm above 1k you should have more voltage on your battery terminals than you have with the engine off. You won't get to the full voltage until the current falls off to near zero and the battery is fully charged.....but you knew that.

I never measured the stator AC (don't forget to change to AC range) output yellow wire(s) voltage at a full battery and WOT but the RMS voltage into the regulator, the voltage a DMM measures, is Root Means Square which is the same as the equivalent DC voltage. Since a couple of diode drops are involved, the AC input to the rectifier would probably read about 16v at WOT with a fully charged battery, or the yellow wires disconnected and your measuring them open circuit...no load on the stator source.

With that said, and I were you, I think my next step would be to remove the stator leads at the connectors, Run the engine rpms up to 1500 (you used 2000...ok) on muffs which is a reasonable rpm and measure the stator output AC voltage. If 14 or so I would consider the stator ok. With that said, possibly the RR module has a corroded wire, maybe not on it since you said you changed it, but if it grounds to a plate and the plate is grounded to the engine block and the battery - is connected to the engine block corrosion could prevent adequate regulation.

Is there a black ground wire with the RR module or does it rely on the aluminum case to get it's continuity back to the battery - terminal through the engine block?

 

[asdasc]

Thank you so much!! I am going back out to the cottage today and will take the measurements. I am really hoping that I don't have to pull the flywheel. I believe that the only ground it to the block, but it is weird that these are painted surfaces. Again, I will double check that as well. I wish I had a voltmeter or ammeter on the dash.