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Stator swap ?

D

Donewright

Regular Contributor
Greetings

-1978 Mercury V6 150hp

The wires on my current stator are in bad condition. It looks like the previous owner made a couple of splices, but the wire covering just crumbles when pressed between the fingers. I have a stator that is in great shape that came off of a blown 80's 150hp mercury XR4. I looked up the specs for both parts and it appears that the only difference is the XR4 stator is rated for 16 amps and the '78 is rated for 9 amps. I want to swap them, but I'm afraid that the higher amperage will burn out the other components.

'78 Stator: http://www.marineengine.com/newparts/part_details.php?pnum=CDI174-5456&ptype=&Engine=&Model=
XR4 Stator: http://www.marineengine.com/newparts/part_details.php?pnum=CDI174-9873-16&ptype=&Engine=&Model=

Would the idea be like a battery? Where the stator can supply up to 16 amps depending on the demand of the load? It does not mean that it will be a full 16 amps at all times. In fact, if the original stator was only 9 amps, then I don't think the load would ever require more than 9 amps from the 16 amp stator??


Any insight?
 
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Maybe I am in left field but electronic logic says it should work as long as the regulator is rated to handle/control the higher output. It's no different than using a 5 amp charger vs. a 10 amp charger on a dead battery. The former is slower than the latter. The same goes for using a 30 amp alternator on an I/O engine vs. a 65 amp alternator. Marine engine charging systems are designed to supply what is necessary for the expected electrical load at maximum RPMs.
 
I don't have a regulator, only a rectifier. So I'm still thinking that as long as the stator physically fits, it will supply the 9 amp draw that my motor would pull at WOT. Although it has a 16amp capacity, it would never be required to supply more than 9.

IMG_2667.jpg IMG_2666.jpgIMG_2664.jpg
 
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If I remember my basic electronics the alternator will put out 16 amps at max RPMs, your engine will use less than 9 amps and the balance will go to the battery. You will have enough amperage to install an isolator and charge a trolling battery. You may fry the rectifier module if it isn't rated to handle 16 amps. You might want to upgrade it.

Anybody else want to chime in w/some expertise? Please do so.
 
That would be awesome! I have located an isolator mounted upside down inside the battery compartment, I was hoping that I would be able to utilize it when moving from spot to spot to top off the trolling batteries.

I'll try to find some ratings on the rectifier ..........
 
What gauge is the RED wire from the rectifier to the starter solenoid? You should increase the ga. (lower the wire number) to handle 16 amps. Clean and seal w/liquid rubber all of the wire connectors and terminals on the rectifier and starter solenoid; they look corroded.
 
The wire appears to be a size 10 which should handle 16 amps.
I can't seem to find any rectifier ratings? There are plenty of replacements to be found, just no specs. I did locate one site that seems to indicate that the stator can be swapped, but I would need to use a regulator instead of the rectifier? I'm not quite sure why, the rectifier appears to be a full bridge so the DC should be pretty good coming out of it. I really don't want to shell out 150 bucks for a new regulator. I have one off of my donor engine but it is HUGE and I have no place to mount it.

Yes, the connections have a little corrosion, it appears the prior owner did some work and never coated the connections. Once I get the wiring completed I will cover them correctly.
 
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Holy crud! The regulator (18-5824) on the donor engine is 40amp and looks like it's nearly 500 dollars! There just isn't anywhere to mount that big of a regulator on this engine :(
I was able to make out the stator part number as 398-9610A3, which when I look it up, it indicates that it is indeed a 40 amp stator!!!!!

This may not be feasible ....... unless I locate a place to mount that enormous regulator... or locate a more modern regulator that is smaller in size Which you recommended earlier). It may end up costing me some cash to make it work. Though it will be cheaper than having to buy the stator too :)

IMG_2671.jpg IMG_2674.jpg
 
Looks like they have smaller sized replacements for the older 40 amp regulator. They look to be about the same physical size as the one currently mounted on the engine. Oh, and I think I determined that my existing rectifier is only 20 amps, which would have been great for the 16 amp Stator! Just my luck, another 100 dollars.

CDI has one: http://www.marineengine.com/newparts/part_details.php?pnum=CDI194-5279&ptype=&Engine=&Model=

new regulator.jpg


Wait..... Why can't I just use something like this to replace what I have instead of getting a whole regulator? It's sealed like my original. I would just have to run a pigtail to ground.
rectifier option.JPG
 
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