95 force 120 ignition question. Need a pro's advice

DonPaulk

Cadet
Joined
May 11, 2014
Messages
9
I have a force 120 that runs perfect at 4000 rpm and below. 4000 rpm pushes 18'welcraft cc 27 knts. over 4000 rpm engine loses fire a cylinder and i limp back to the dock. both times this has happened,after i get home to troubleshoot i can find nothing wrong. all 4 cylinders fire and boat runs perfect again. replaced switchbox,same problem.
I am a pretty fair mechanic,i build harleys and drag cars along with boat work, mine as well as others. this intermittent problem is making me crazy because i can not catch it in the act when it drops out. its really hard to check fire in rough chop in the bay.
what are the chances the high speed stator has a bad coil or possibly the trigger or CDI?
it seems that heat may be what is causing the failure because after a couple hours it runs perfect again until 4000 rpm is exceeded for a couple min.
I have a clymer manual but it is mostly about every other motor force makes. shows at least 6 different ignition systems.
I am probably being rash but the clymer manual is as usless as an automotive haynes manual.
I hope i have explained it clear enough that someone would have an idea of what is going on. i am thinking the high speed stator is failing.
i am going to read the manual cover to cover and look for a testing procedure for the stators, pull the flywheel and inspect magnets, and ohm the trigger wires. not sure how to check the cdi.
any help is welcomed
 

pnwboat

Rear Admiral
Joined
Oct 8, 2007
Messages
4,251
Re: 95 force 120 ignition question. Need a pro's advice

Not sure that I'd consider myself a pro, but I'll give you a couple of things to check.

Sounds like you have the Mercury style Thunder Bolt ignition system that uses the Switch Box.

Possible bad voltage Rectifier/Regulator. Disconnect the two Yellow wires that come from underneath the flywheel that go to the voltage Rectifier/Regulator. Tape them off so they don't short out to anything or get caught in the flywheel. See if that makes any difference. NOTE: If the Rectifier/Regulator is working correctly, you should see about 14.5 VDC at about 2000 RPMs on the Red wire on the Rect./Reg.

On the 1995 motors, there were a couple of stators that might have been used. If you have a high and low speed winding stator, you should have a Blue and a Red stator wires. I don't know which is which, but disconnect the stator wires and measure from the Red wire to ground, then the Blue wire to ground. On one, you should see 3250 - 3650 OHMs. On the other 75 - 90 OHMs to ground.

If you have the other type of stator with just one winding, you should have a Blue and Yellow wire coming out from under the stator. Disconnect the Blue and Yellow stator wires and read between the two (not to ground). You should see 680 - 850 OHMs.
 
Last edited:

Jiggz

Captain
Joined
Oct 23, 2009
Messages
3,817
Re: 95 force 120 ignition question. Need a pro's advice

Ditto on isolating the regulator first.
 
Last edited:

pnwboat

Rear Admiral
Joined
Oct 8, 2007
Messages
4,251
Re: 95 force 120 ignition question. Need a pro's advice

Good catch there Jiggz. I've corrected my mistake.
 

DonPaulk

Cadet
Joined
May 11, 2014
Messages
9
Re: 95 force 120 ignition question. Need a pro's advice

thanks guys. I'll check it out tomorrow and let you know what i find:joyous: i am going out to check it and remember there being 2 red wires on reg/rect. the larger diameter is hooked up, the smaller is hooked to nothing. also have a purple from under flywheel with a rubber plug,hooked to nothing.

i also have a 23 foot mako cuddy cabin with johnson ocean runner 200. previous owner replaced the power pak and used but splices on some wires to the reg. had a strand of wire outside the but splice grounding intermittently.
why someone would use but splice on something so critical over solder and heat shrink is beyond me.

I'll be back.......
 
Last edited:

DonPaulk

Cadet
Joined
May 11, 2014
Messages
9
Re: 95 force 120 ignition question. Need a pro's advice

this is what i have found so far:mad: 2000 rpm both red wires from reg show 12.5 vdc.
after chasing all the wires,it looks like i have a red and grey for the stator.
using a fluke 113 dvm set to ohms in auto range:
red to ground-open
grey to ground-2.683 ohm
red to grey-open
grounded temp input wire and alarm works,figured while i was there....
looking under the flywheel... all but two coils are newer open windings, the two are sealed.
it seams that there may be one or more things happening.
i need a wiring diagram for whatever ignition system this is.

i will never buy another american made outboard.
i have had yamaha and suzuki motors that i could not break and trust me if there is a weak link I WILL BREAK IT ON PURPOSE BECAUSE I WANT DEPENDABILITY.
when i build a drag motor, i run it thru a break in time them i put it on the pavement and try to blow it up. if i cant break it,its ready to race. if it scatters,well then i must have not done it right. its costly but very effective in the dependability and consistency of winning.

found the schematic,
had my head up my @$$
gona start over
still 12.5 at reg/rect
all stator coils open
CDI p/n 174-8778k1
 
Last edited:

pnwboat

Rear Admiral
Joined
Oct 8, 2007
Messages
4,251
Re: 95 force 120 ignition question. Need a pro's advice

According to the CDI WEB site, that stator CDI P/N 174-8778K1 was only used on the 120HP motors up to 1992.

Doesn't mean that it won't work, but the stator for the 1995 120HP motor is P/N 174-9710K1. Attached is the link for the installation guide for the 174-9710K1. Take a look at it and see if the wire color codes on the Switch Box matches yours.

http://www.cdielectronics.com/wp-content/uploads/2014/05/IS-174-9710K-1.pdf

I suspect that a previous owner may have replaced some components with the incorrect one's but it's kind of hard to tell at this point. It does appear that your stator has an open winding. Red to ground OPEN.

That 12.5 volts on the Rectifier/Regulator is just reading battery voltage. Are the two Red wires on the Rect./Re. actually connected to wires on the harness, or is just one of them connected? If both are connected to wires in the harness, then it's probably bad. If only one of them is connected and the other is just hanging loose, then tie both of them together and measure voltage again. One of those red wires is a "sense" wire. If it's not connected to the battery, the Rec./Reg. will not work.

As far as dependability, you'll find that there are many Force motors out there that are 25+ years old and running just fine. Definitely not as sophisticated or as powerful as the newer outboards, but with proper care, they run for a very long time without costing you an arm and a leg if you're a DIY'er.
 

DonPaulk

Cadet
Joined
May 11, 2014
Messages
9
Re: 95 force 120 ignition question. Need a pro's advice

yep high and low speed coils are open
the charging loop (yellow wires) reads 1 ohm on auto range (fluke 113)
the stator is shot.
the purple wire i found is switched b+ and not used
as for the red wire,it was hanging behind the coil packs. i agree with you about hooking it to battery power.
i have got a stator on the way. thanks for the help. the link explained almost exactly its behavior.
i found a stator but it has upgrade mod with it. "174-8778K1 CDI upgrade 834949A2". would anyone know what this mod does?
 

pnwboat

Rear Admiral
Joined
Oct 8, 2007
Messages
4,251
Re: 95 force 120 ignition question. Need a pro's advice

I'm not 100% sure, but many years ago I believe that the upgrade is an adapter that maybe goes to the high speed winding of the stator to prevent it from burning up. Instructions should come with it that explains the hook up. If it's what I think it is, the adapter has two input wires and two output wires plus a ground. It's about the size of a candy bar and is often referred to as "the candy bar". It's been a while and the brain is not as sharp as it used to be!

Here is a link to a picture of the adapter. It has the 834949A3 part number on it.

Mercury Force Outboard Stator Adaptor 834949A3 834949A1 8M0021546 Works Perfect | eBay


1 OHM resistance is about normal between the two yellow battery charging wires. It's typically .6 OHMs depending on your meter.
 
Last edited:

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,657
Re: 95 force 120 ignition question. Need a pro's advice

OK, kind of got lost in all the meter readings - too tired , sorry.

But, early on, you mentioned heat related spark loss.
Have you verified that the coils are all good?
 

DonPaulk

Cadet
Joined
May 11, 2014
Messages
9
Re: 95 force 120 ignition question. Need a pro's advice

i am thinking that the stator wasnt working at all. engine power loss over 4k rpm may be that engine not charging. and battery power dropping too low to maintain spark at high speed. both high and low speed coils read open, no output voltage. as discussed before, sense wire from regulator was never hooked up.
at this point i have stripped the wiring harness and cleaning all connections and applying de ox to stop corrosion.
this really is a great motor,less than 200 hours, very clean under the cowl. it has had bad mechanics working on it. i have replaced the carbs because they looked like they were beat with a hammer. it reminds me of an old commercial on tv with a chimp and sledge hammer. i broke 2 wheel pullers taking the flywheel off. think the guy i got it from worked on it last and could not get the flywheel off and beat on the motor.(like that makes it bend to his will?) hammer mechanic is what we call them.
with it running badly,3800rpm pushes my 18' welcraft cc 27 mph. at wot its close to 40 mph but drops out after maybe 5 min. engine does not run hot. can feel no abnormally hot coils. overheat alarm works.
i have been out trolling 30 mile round trip with no problems unless i take it over 4000 rpm or battery dies.
I am just gona replace stator and regulator. already have new switch box.
 
Last edited:

pnwboat

Rear Admiral
Joined
Oct 8, 2007
Messages
4,251
Re: 95 force 120 ignition question. Need a pro's advice

The ignition system is self energizing. The only purpose of the battery is to operate the starter and any electrical accessories (and overheat alarm). If the battery is dead, you can take a rope, put a knot on one end and wrap it around the flywheel (there should be some notches in the outer circumference to catch the knot) and pull start the motor. It'll run fine without any battery power.
 

DonPaulk

Cadet
Joined
May 11, 2014
Messages
9
Re: 95 force 120 ignition question. Need a pro's advice

Just found it had a 6 amp stator. just looked it up by serial number and it requires a 16 amp stator. the 6 amp probably didnt last long. if demand was up to 16 amps and all it could give was 6.
when i am not goofing around, I am an industrial instrumentation/controls electrician. 25 years worth.
 

DonPaulk

Cadet
Joined
May 11, 2014
Messages
9
Re: 95 force 120 ignition question. Need a pro's advice

The ignition system is self energizing. The only purpose of the battery is to operate the starter and any electrical accessories (and overheat alarm). If the battery is dead, you can take a rope, put a knot on one end and wrap it around the flywheel (there should be some notches in the outer circumference to catch the knot) and pull start the motor. It'll run fine without any battery power.

interesting... when the battery is weak, it runs like crap. it acts like a car with a bad alternator. i think the last guy to work on it may have fried the reg and stator because of how it acts and the condition of hammer marks on the carbs
 
Last edited:

pnwboat

Rear Admiral
Joined
Oct 8, 2007
Messages
4,251
Re: 95 force 120 ignition question. Need a pro's advice

If the rectifier is bad, it can affect the high speed operation of the motor. It doesn't really have anything to do with the battery voltage itself. Since the rectifier is no longer working and not charging the battery it may appear that the low battery may be affecting the way it runs when in fact it's actually the rectifier that's causing the problem.

I believe that the Red stator wire is the high speed winding. Your resistance measurements measuring Red to ground was open. That would seem to confirm that the high speed winding is bad. As long as you keep the RPMs below around 3000, everything is OK. That's my theory anyways. Seems to kind of fit your symptoms.

As far as the difference between the 9 amp and 16 amp stators....I mentioned before that I thought that the previous owner may have put the wrong stator on the motor. The CDI stator P/N you referenced 174-8778K1 is the 9 amp version. The 16 amp version is P/N 174-9710K1.

By the way, it looks like the CDI replacement stators do not require the adapter.
 
Last edited:

DonPaulk

Cadet
Joined
May 11, 2014
Messages
9
Re: 95 force 120 ignition question. Need a pro's advice

i agree totally. i am gona bite the bullet and replace the stator and regulator. i also found a note that i have to use regulator cdi p/n 194-5279 with the stator P/N 174-9710K1.
Trust me its cheaper to fix than replace and Moma likes to fish too,and if Moma aint happy,........

Anyhow,thanks to everyone for the answers.
parts ordered, in the meantime i am going thru the wire connections
 
Top