Mercury 70 hp outboard - stator question

kacox65

Recruit
Joined
Nov 26, 2009
Messages
5
I am replacing the stator and trigger assembly on a 1981 70 HP Mercury outboard (serial 5755495). I have the new parts and noticed that the stator is different. The old one has two yellow wires, 1 red, 1 blue, The new one has the same wires plus a black wire (ground??). The red/blue wires on the new one are shorter than the old, by about 3 inches. When I set the new stator in the same orientation as the old, the red/blue wires don't reach. If I rotate the stator 180 degrees it will seat correctly and the wires will reach the ignition box, but not sure this is right, wouldn't this affect the timing? Also there are some markings that are punched into the the top of the stator. They are probably telling me something, but I don't know what. Both are circles with hash marks on the inside and an arrow in the middle pointing to one of the hash marks. Once circle has 12 hash marks and the arrow is pointing to the 7. The other has about 30 hash marks and the arrow is pointing to the 10. Did some engineer figure out you could reorient the stator to save money on wire length, or do I have the wrong part? I looked up the replacement part (Sierra - SIE18-5865 for Mercury - 398-5704A7) . This should be the replacement for my motor.

Thanks

Kevin
 

RaScLeS

Petty Officer 1st Class
Joined
Jun 27, 2009
Messages
230
Re: Mercury 70 hp outboard - stator question

I to have replaced both those parts but had a mechanic do it unfortunatley. some colours look to be different but everything "reachs" just fine. double check the part #.

so far ive got the new parts in and power is revealed only at wide open. so maybe this spring ill get some luck:(
 

kacox65

Recruit
Joined
Nov 26, 2009
Messages
5
Re: Mercury 70 hp outboard - stator question

rascles

Thanks for responding... So when looking at your repaired motor, Is the stator mounted so that the wires come out of your stator on the carburetor end or the spark plug end? The wires reach for my new stator only if it is mounted such that the wires come out the spark plug end. and how many wires do you have coming out of your stator? My new one has 2 yellow a red, a blue and one "new" black wire. There is a place to secure my "new" black wire to ground in the orientation I described above. I'm thinking this is alright, as I believe that stator is primarily for charging, so it's orientation is not as critical as the trigger assembly. Is your engine old like mine (1981)?

Thanks
 

ajgraz

Lieutenant Commander
Joined
Mar 1, 2010
Messages
1,858
Re: Mercury 70 hp outboard - stator question

Kind of reviving an old thread here, but not too old...

So your new stator is part number 398-5704A7? That's what's supposed to be on there according to the parts lists.

Was your old stator part number 398-5704A2 by chance? Did it ever run correctly with the old stator?

I am curious because I am contemplating the opposite...putting a newer 398-5704A7 (about 1980+) stator on my older (1978) 3 cyl 70hp, which specifies a 398-5704A2 stator. The only difference I can see is that the A7 (and the A5, which was apparently a late 1979 change) has that black ground wire, where the A2 did not. All the stator resistance checks are the same between all three of these part numbers, and as you've demonstrated they physically fit regardless of year--although perhaps with a 180 degree rotation.

Anyone see a reason why I should not try putting a 398-5704A7 stator on my 1978?

No one really answered this question: Does anyone foresee any issue with rotating the stator 180 degrees?

398-5704A2:
!Bjbdvp!B2k~$(KGrHqUH-CsEs-R1)8iDBLTh9GPRe!~~_35.JPG


398-5704A7:
!BbGb6tQCGk~$(KGrHgoOKjwEjlLmS!t7BKuYYvpK3w~~_35.JPG


(Clearly shows the shorter wires on the A7, as the OP mentioned; as well as the black ground wire)

I wonder why they added the ground wire later? Perhaps the stator body didn't ground well enough through the mounting bolts?
 

RaScLeS

Petty Officer 1st Class
Joined
Jun 27, 2009
Messages
230
Re: Mercury 70 hp outboard - stator question

lol ill bump this,

spring is here and my motor still runs ****. any luck with either of you ?
 

j_martin

Admiral
Joined
Sep 22, 2006
Messages
7,474
Re: Mercury 70 hp outboard - stator question

lol ill bump this,

spring is here and my motor still runs ****. any luck with either of you ?

You should work up your motor from scratch. Check compression, spark, and fuel delivery, then do a complete link-n-sync. Also check any bleed hose routing, condition, and the check valves.

If it idles, don't worry about reeds.

hope it helps
John
 

ajgraz

Lieutenant Commander
Joined
Mar 1, 2010
Messages
1,858
Re: Mercury 70 hp outboard - stator question

lol ill bump this,

spring is here and my motor still runs ****. any luck with either of you ?

I should know more sometime soon.

My 1978 70hp is getting some much-needed and much put-off overhauling, and I've been on an EBAY spree lately.

My compression tests good.
Internal engine harness: corroded to all hell and has an intermittent short in the connector; got tired of patching it up, so I'm making a new one from scratch.
Fuel delivery: recently re-did carbs, filter, pump, and new check bulb.
Spark: something's still making it lose power/cutout at above 2500rpm. Got the special flywheel puller tool and removed the flywheel to check out stator and trigger wiring, figuring they might be corroded, too. Bias wire on the trigger and most of the wires on the stator were corroded to just a wispy green thread, right at the body of each piece; no way to fix, so I got me a NOS 68162A6 trigger (funny, what's supposed to be a brown wire is purple with a brown flag on it), and a NOS 398-5704A7 stator (see earlier post; I think it should work). Also got a DVA adapter so I can check these out once installed.
Link-n'-sync: really not possible until I get all this other stuff squared away; found an unbeatable deal on a replacement flywheel with a readable timing sticker, too ;) (was always kinda guessing on timing before)
 

RaScLeS

Petty Officer 1st Class
Joined
Jun 27, 2009
Messages
230
Re: Mercury 70 hp outboard - stator question

damn if i have to do much more work to this motor im done with it.

im hoping the turn of a screw on the carbs fixes it, basically it stinks, smokes, and leaves the pale of water black and grimey to hell. and it also stinks.....basically like this mercury. still hoping for the best for mine and everyone elses 70hp's of hell
 

dtmc78

Cadet
Joined
Jul 1, 2008
Messages
15
Re: Mercury 70 hp outboard - stator question

I have an old '78 3cyl 70hp..went through same problem..cuts out around 2500rpm. Did everything, rebuilt carbs too..took to mechanic because did not have a fly wheel tool. Asked them to replaced my trigger and do time'n. He also changed out my merc switch, said that was part of the problem..might have been main cause from cuting out at 2500rpm. Been running strong for a 1 1/2 seasons. Good luck.
 

turtles11756

Petty Officer 1st Class
Joined
Dec 5, 2007
Messages
260
Re: Mercury 70 hp outboard - stator question

i replaced stator on a mid 70's (4829645) 70hp merc . original stator pt#398-5704A2 with CDI part #174-5454K1 . install instructions "mark position of the mounting screws in relation to where the stator wires come out of old stator" . "orient and install the new stator in the same position as the old stator". the wires on the CDI part were correct length and the motor has a real hot spark again
 

ajgraz

Lieutenant Commander
Joined
Mar 1, 2010
Messages
1,858
Re: Mercury 70 hp outboard - stator question

I have an old '78 3cyl 70hp..went through same problem..cuts out around 2500rpm. Did everything, rebuilt carbs too..took to mechanic because did not have a fly wheel tool. Asked them to replaced my trigger and do time'n. He also changed out my merc switch, said that was part of the problem..might have been main cause from cuting out at 2500rpm. Been running strong for a 1 1/2 seasons. Good luck.

Interesting thing: Just after posting above I took a good look at this new old stock trigger I bought. It's marked as made in 1978, it obviously hasn't been used, has just been sitting in a box for 30-odd years. However, the insulation on the bias wire (white w/black) is brittle and crumbly where it was exposed to the air. I think whatever Mercury used for insulation on that particular wire so many years ago does not age well--it was also the bias wire (probably the insulation first) that failed on my original trigger. I'm thinking to butt-joint/heat shrink in some fresh 18 gauge Ancor marine wire for the bias before I install it.

Somewhere in my web surfing, though I forgot to bookmark it, I came across a site where a guy used an oscilloscope to determine what happened if you shorted or diconnected the bias wire; I don't remember the specific details, but the upshot is that it threw off the synchronization of the trigger signal in the switchbox such that it was the same as advancing the spark timing by 25 or 30 degrees. :eek:

CDI's trigger assemblies do not cross reference to these motors prior to 1980 model year...not to say they wouldn't work, though. If this trigger can't cut the mustard, I may have try one, since I'm sure Mercury Marine hasn't made these triggers for decades. My concern is that the p/n for the flywheel changed in 1980, so using a 1980+ trigger might throw off the timing if the hub magnets are oriented differently. I think the 1977-1979 70 hp's, with their unique harness and orphaned parts availability, are truly the ones from hell.

turtles11756 said:
i replaced stator on a mid 70's (4829645) 70hp merc . original stator pt#398-5704A2 with CDI part #174-5454K1 . install instructions "mark position of the mounting screws in relation to where the stator wires come out of old stator" . "orient and install the new stator in the same position as the old stator". the wires on the CDI part were correct length and the motor has a real hot spark again

If my experiment with a 1980+ stator on my 1978 does not work out, I'll be getting a CDI stator.
 

kacox65

Recruit
Joined
Nov 26, 2009
Messages
5
Re: Mercury 70 hp outboard - stator question

Finally got this finished, although haven't run it under load, but it idles well at around 1600-1700 rpm. Makes sense now after reading these posts that Sierra pulled the ground out to a separate wire, so that explains the mysterious fourth wire. My motor hasn't seen alot of hours even though it is old, so hoping this will be the last thing I'll have to do for a while.
 

chum1

Petty Officer 1st Class
Joined
Apr 15, 2010
Messages
359
Re: Mercury 70 hp outboard - stator question

Just finished repairing the wiring on the trigger of a 77' 85hp and came across the same thing with the black/wht wire crumbly insulation, on my trigger the colors were white,white/blk,vilot,brown, some one used some cheap butt splices and household wire on these wires and also some of the stator wires,( probably one of the reasons for no sparky on #4 and a no charge condition)

I found that when using these splices in a high vibration area they will soon fail intermittently and are very difficult to troubleshoot the best way to join them is a soldering paste, solder and some heat shrink.. The trigger assy. moves with the throttle so wire failure is eminent unless properly joined and secured with some play for movement.

here is a pic of what not to do.
 

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CDI Tech Support

Petty Officer 2nd Class
Joined
May 14, 2010
Messages
127
Re: Mercury 70 hp outboard - stator question

So your new stator is part number 398-5704A7? That's what's supposed to be on there according to the parts lists.

Was your old stator part number 398-5704A2 by chance? Did it ever run correctly with the old stator?

I am curious because I am contemplating the opposite...putting a newer 398-5704A7 (about 1980+) stator on my older (1978) 3 cyl 70hp, which specifies a 398-5704A2 stator. The only difference I can see is that the A7 (and the A5, which was apparently a late 1979 change) has that black ground wire, where the A2 did not. All the stator resistance checks are the same between all three of these part numbers, and as you've demonstrated they physically fit regardless of year--although perhaps with a 180 degree rotation.

Anyone see a reason why I should not try putting a 398-5704A7 stator on my 1978?
Our 174-5454K1 stator will replace a vast array of 398-5454 part numbers, so no need to guess which Mercury "A" number will work:

CDI Part Cross Reference

No one really answered this question: Does anyone foresee any issue with rotating the stator 180 degrees?
Stators can be rotated two bolt holes (or multiples of two) in any direction.

I wonder why they added the ground wire later? Perhaps the stator body didn't ground well enough through the mounting bolts?
CDI stators are grounded through their frame.
 

CDI Tech Support

Petty Officer 2nd Class
Joined
May 14, 2010
Messages
127
Re: Mercury 70 hp outboard - stator question

Interesting thing: Just after posting above I took a good look at this new old stock trigger I bought. It's marked as made in 1978, it obviously hasn't been used, has just been sitting in a box for 30-odd years. However, the insulation on the bias wire (white w/black) is brittle and crumbly where it was exposed to the air. I think whatever Mercury used for insulation on that particular wire so many years ago does not age well
You are correct. The wire that Mercury & OMC used in those days...the insulation was manufactured poorly. We've gotten hundreds of calls over the years from guys wanting to replace a part (usually the harnesses) because of insulation that has fallen off or starting to crumble.

Somewhere in my web surfing, though I forgot to bookmark it, I came across a site where a guy used an oscilloscope to determine what happened if you shorted or diconnected the bias wire; I don't remember the specific details, but the upshot is that it threw off the synchronization of the trigger signal in the switchbox such that it was the same as advancing the spark timing by 25 or 30 degrees.
The bias wire (White/Black or solid Black) from the trigger is used to sync it with the switch box, so that theory is more or less correct.

CDI's trigger assemblies do not cross reference to these motors prior to 1980 model year
Not true.

Application Guide - Mercury

Our trigger replacement for a Mercury 70HP 1977-1987 is part# 134-6453 List price is $178.00. We sell direct or can be purchased through iboats.
 

RaScLeS

Petty Officer 1st Class
Joined
Jun 27, 2009
Messages
230
Re: Mercury 70 hp outboard - stator question

well looks like everyone is on track and im still catching up! trying to get out this week my new trigger failed (white wire wont produce spark) so replacing with an old one.

shouldnt have to learn so much about a motor!!! very unrelaible
 

RaScLeS

Petty Officer 1st Class
Joined
Jun 27, 2009
Messages
230
Re: Mercury 70 hp outboard - stator question

Just finished repairing the wiring on the trigger of a 77' 85hp and came across the same thing with the black/wht wire crumbly insulation, on my trigger the colors were white,white/blk,vilot,brown, some one used some cheap butt splices and household wire on these wires and also some of the stator wires,( probably one of the reasons for no sparky on #4 and a no charge condition)

I found that when using these splices in a high vibration area they will soon fail intermittently and are very difficult to troubleshoot the best way to join them is a soldering paste, solder and some heat shrink.. The trigger assy. moves with the throttle so wire failure is eminent unless properly joined and secured with some play for movement.

here is a pic of what not to do.

this is a big no no from what ive read but hope its working for you!
 
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