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Merc 402 charging issues...???

C

chriscraft

Member
Would anyone know what the voltage should be on a Merc 402 when running well above idle? My volt gauge reads 12.4 - 12.5 and my hand held meter reads the same. I checked at the battery, both running and not running, and I checked it at the solenoid. All reading the same. I also have a question regarding the rectifier. Is it located under the flywheel? I found the 2 wires (red and blue) that come out of the stator and to the terminals on the switch box but per the schematic, there should be 2 yellows along with them that go to the rectifier and one coming out of the rectifier to the starter solenoid. I'm thinking that this might be a variation. i'm guessing that this engine is not charging.
Any ideas?

Thanks

Mark
 
After looking around other sites, I have noticed that in regards to ignition parts, stators and rectifiers.... manual start engines show N/A in reference to a rectifier. My engine is a rope star but outfitted with a starter. There are NO yellow wires coming out of the stator at least visible from the out side. Could the issue be that this particular model has no charging system?
 
Rectifiers are mounted on the side of the motor not under the flywheel. It sounds like someone may have added a starter but not the charging system.
 
I see that. It would go to the battery via the starter solenoid. Next question, Is it possible to retro fit with a rectifier? Can power be pulled from the blue or red wires coming from the stator?
 
No. Those are for ignition only. You'll need a new stator assembly (and possibly flywheel) that's designed for charging.

Jeff
 
pic of new style charge stator, stator and trigger, 3 separate pieces
old stator assembly had charge coil and stator as one unit

pic of rectifier on front, 83 40hp
 

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You definitely have a charging circuit set up. Note the rectifier in the photo.

Jeff
 

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Very good information guys. Thanks alot. I'm going to peruse some part numbers and see a) if I have the correct flywheel b) procuring the proper stator c) how much this will cost. I really can't see sinking 500.00 dollars into this old motor. I will just charge the batteries every time I bring the boat home.

Thanks again
 
..."Hey Jeff, thats my engine, just showing him what to look for......jb "

Well, now he knows!

Jeff

PS: Just for the record, the charging systems on old Mercs like that are little more than trickle chargers.
 
Thanks again....one last question. In your honest opinion, would it be worth retrofitting this engine with a charging system? Or should I just put the benchtop charger on it at the end of the weekend?
 
I think I would have to agree. I just like to see all systems working properly. On another note, how does this motor (402) rate in the grand scheme of things? Were they a dependable, reliable motor? What issues were inherent with them? I know this one that I own isn't very economical.

Just curious.

Thanks
Mark
 
keep the starter tight, it likes to break the mount when loose.

Lube the drive shaft splines lightly when changing the water pump every 2 years. service the lower unit yearly.

Your engine dates back to the mid 70's, economical, I think its done pretty well to still be ticking. It should get 6 miles/gal at mid throttle on a jon boat if pitched right.
 
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