1991 70 HP Force Little or no spark

[Farmerbouy]

Hi everyone,
I have been impressed with the knowledge contained in these forums.
I need some help with a 1991 70 HP Force.

It has been getting harder and harder to start.
Took it out to the lake and got it running and then stopped the engine for a bit.
Would not start. Has fuel and the carb has been removed and cleaned.
I have did a spark test and if I set my spark tester really close I can see a weak spark.
Also if I ground the removed spark plug i can see a tiny blue spark.
Have a good battery connection battery is putting out about 12.7 - 13 volts.
When attempting to start the motor is definitely turning the required 250 RPM.

I took all of the stator and trigger wires loose and run an ohms test.
Here is what I have so far.
I do not have a DVA adapter at the moment.

I have Control Box has P/N 332 7778A10 on it.
The stator looks like the original black one.
Couldnt fine the P/N on it.

Here are the resistance readings from the stator and trigger wires.

Red Stator to Engine Gnd - 138 ohms
Blue Stator to Engine Gnd - 2,234 ohms

Yellow to Engine Gnd - 9m ohms
Yellow to Engine Gnd - 9m ohms


Trigger wires
Violet to Engine Gnd - 15,500 ohms
White to Engine Gnd - 15,500 ohms
Brown to Engine Gnd - 15,500 ohms

Violet to White/Black - 1,200 ohms
White to White/Black - 1,200 ohms
Brown to White/Black - 1,200 ohms

I haven't figured out how to test the coils yet.

Also I have tried the starting with the yellows unhooked from the rectifier.
And also with the stop circuit disconnected (black/yellow).
No change

Can anyone tell me if any of those numbers look amiss?

Thanks
Lynn Nightingale

 

[pnwboat]

Re: 1991 70 HP Force Little or no spark

Stator resistance windings should be as follows:

Blue to engine ground - 3259 to 3650 ohms.

Red to engine ground - 75 to 90 ohms.

I would say that your stator has some bad windings. There is also a possibility that the switch box P/N 332 7778A10 may also be bad, but you won't know for sure until you replace the stator.

 

[Farmerbouy]

Re: 1991 70 HP Force Little or no spark

Stator resistance windings should be as follows:

Blue to engine ground - 3259 to 3650 ohms.

Red to engine ground - 75 to 90 ohms.

I would say that your stator has some bad windings. There is also a possibility that the switch box P/N 332 7778A10 may also be bad, but you won't know for sure until you replace the stator.

Thanks for the quick reply!
I will try a new stator.

Is there a better stator to buy other then the stock one?
Looks like Force did an update on them at some time or another.

Thanks again.

Lynn

 

[pnwboat]

Re: 1991 70 HP Force Little or no spark

Just realized that the stator on you motor came in two versions. One version has Blue and Blue/White, Red and Red/White stator wires. The other version has just a Blue and a Red stator wire with a separate ground wire.

If you have the first version, you check resistance between the Blue and Blue/White wires, Red and Red/White wires. If you have the second version, then you checked the resistance correctly. Sorry I didn't think of that earlier.

As far as replacements, I don't think the OEM type stators are that readily available. CDI electronics makes an aftermarket replacement and has a good reputation for reliability, and includes installation instructions because the wiring may be slightly different than the factory stators. CDI P/N you need is 174-9710K 1. They are available here on IBoats and other sites.

 

[Farmerbouy]

Re: 1991 70 HP Force Little or no spark

Stator resistance windings should be as follows:

Blue to engine ground - 3259 to 3650 ohms.

Red to engine ground - 75 to 90 ohms.

I would say that your stator has some bad windings. There is also a possibility that the switch box P/N 332 7778A10 may also be bad, but you won't know for sure until you replace the stator.

Thanks for the quick reply!
I will try a new stator.

Lynn

 

[Jiggz]

Re: 1991 70 HP Force Little or no spark

Let me pitch in my 2 cents before you jump on the gun on the new stator. When reading resistance either between wires or to ground make sure at least one of the wires is disconnected from the ckt or terminal board. This is to ensure accurate reading. The stator readings according to the manual should be between 2900~3650 ohms from either blue and red wire to ground. In your particular case you need to at least disconnect both red and blue wires from the ckt before taking resistance readings. However, if you already did this and the readings are still the same, then it is time to remove the flywheel and inspect the stator winding. Any sign of overheating indicates fault and replacement is required.

 

[Farmerbouy]

Re: 1991 70 HP Force Little or no spark

I have the stator with me here in my lazy boy.
I have my Fluke 77 meter for testing.
I have 109 Ohms on the Red wire to the black wire.
I have 2350 Ohms on the blue wire to the black wire.

No sign of over heating on the stator.
I do have a new one coming and if I understand CDI information right I have to install an updated rectifier/regulator as well.
So I ordered one of those too.

Thanks to all.
Lynn

 

[Farmerbouy]

Re: 1991 70 HP Force Little or no spark

OK The new stator and the rectifier/ regulator showed up on Fedex this morning.
Installed per drawings that was sent with it.
Now I have spark on all 3 plugs!
Attempting to set the timing now.
When I have the throttle in WOT position and crank the engine over and look at the timing mark with the timing light the white line that I drew on the flywheel doesn't stand still with the light on it. Sometimes i see it flash early and then late.. It is like it is walking all over the place as I am cranking. I just bought the timing light from Autozone. the best one they had there a digital one.

What would cause the firing not to be consistent?
The trigger module? Or the control box?

Any help diagnosing this would be appreciated.

Thanks
Lynn

 

[Farmerbouy]

Re: 1991 70 HP Force Little or no spark

Just realized that the stator on you motor came in two versions. One version has Blue and Blue/White, Red and Red/White stator wires. The other version has just a Blue and a Red stator wire with a separate ground wire.

If you have the first version, you check resistance between the Blue and Blue/White wires, Red and Red/White wires. If you have the second version, then you checked the resistance correctly. Sorry I didn't think of that earlier.

As far as replacements, I don't think the OEM type stators are that readily available. CDI electronics makes an aftermarket replacement and has a good reputation for reliability, and includes installation instructions because the wiring may be slightly different than the factory stators. CDI P/N you need is 174-9710K 1. They are available here on IBoats and other sites.

I got the P/N 174-9710 1 stator in the mail today.
Also a new Voltage Regulator/Rectifier module CDI 194-5279
Boat still wont start. I have good spark at 1/2" on spark tester now.

After looking at the parts breakdown here I see that I have this motor that uses Stator P/N 398-8778A25
The 1991B - 1992C
See link:
Force 70 HP (1991-1995) IGNITION COMPONENTS (1991B - 1992C) Parts

Is the one that I installed compatible?

Thanks
Lynn

 

[pnwboat]

Re: 1991 70 HP Force Little or no spark

Yes it's compatible. The only difference is the stator battery charging output current. That's why you need match the voltage regulator with the stator output current. CDI P/N 174-8778K 1 puts out 9 AMPs and the CDI P/N 174-9710 1 output is 16 AMPs to charge the battery.

You are correct in your assumption that the inconsistent spark is most likely either the trigger or the switch box. To be sure though, disconnect the stator wires going to the regulator and see if that has any affect on the inconsistent timing. The trigger feeds the timing signal to the switch box which in turn fires the coils. The trigger is just a coil of wire and it ohms out OK. Double check the trigger wires to make sure that the insulation is not broken exposing any bare wires.

 

[Farmerbouy]

Re: 1991 70 HP Force Little or no spark

Can bad insulation cause trigger problems?
I see about 1/4" above the eyelet that fastens to the CDI bow the insulation looks like it is really soft and there is a little bare wire showing. It isn't grounding to anything so I presumed it wasn't a problem. I will try installing new wires and ends and see what happens.
Thanks for all the input.
Lynn

 

[pnwboat]

Re: 1991 70 HP Force Little or no spark

As long as the wires aren't touching anything, it's probably OK. If you have corrosion or frayed ends on the trigger wires, it may be a problem. Regardless, replacing the connectors on the end of the wires is probably not a bad idea. The trigger signal is a pretty small pulse even when it's working correctly. Doesn't take much to affect it.

 

[Farmerbouy]

Re: 1991 70 HP Force Little or no spark

As long as the wires aren't touching anything, it's probably OK. If you have corrosion or frayed ends on the trigger wires, it may be a problem. Regardless, replacing the connectors on the end of the wires is probably not a bad idea. The trigger signal is a pretty small pulse even when it's working correctly. Doesn't take much to affect it.

I did replace the wire ends on all of the trigger wires.
Now the boat starts and runs at fast idle and above.
When i bring it to an idle it dies.
I think i have the throttle and timing out of wack.
Either that or there is something wrong with my idle circuit.
The only way i can get it to idle at 750 - 800 RPM is i advance the timing way ahead.
If it is idling and i check the timing it is running something like 18 - 20 degrees advanced.
Which when i rev it up it will be way too much advanced.
Can someone tell if there should be any advancement of the timing during idle?
I cant do a WOT timing adjustment till i can back it in to the lake on my trailer.

Wonder if anyone has a you tube or a step by step of setting the throttle linkage on this particular motor.
Shouldn't the boat idle with the butterfly in the carb completely closed? then when you advance the throttle it immediately starts open the butterfly?
Maybe i need to take the carb off and clean it up again.
This particular engine has 3 cylinders and one carb.
I have tried messing with the idle adjustment from 3/4 turn out to 2 turns out.
Nothing seems to help.
I think i might be fighting a fuel mixture problem now.

Any ideas?

I appreciate all the input that I have received here.

thanks again!

Lynn

 

[pnwboat]

Re: 1991 70 HP Force Little or no spark

There really aren't any published timing specs at idle. The timing should be set to 30? advanced at WOT. I've checked the timing myself at idle speed and it's usually around 2 or 3 degrees advanced, but that all depends on how far open the throttle is open to get it to idle at the desired speed. It's a little different for each motor.

Have you checked the compression?

 

[Farmerbouy]

Re: 1991 70 HP Force Little or no spark



Good Evening everyone,

Good news and bad news.
Got the boat running.
I had to really turn in the idle adjustment to get it to idle @ 1000 RPM with muffs on.
As you can see in the picture the marl on the cam is about 1/4" below where it should be.
The butterfly is partially open.
Idle air/fuel adjustment is about 1 1/2 rounds open.

At WOT with the plugs removed I have the timing set at 30 degrees advanced.
When it is idling it is around 10 degrees.

I told myself something is wrong here.

Got my compression tester out and checked compression.
Now i know why the goofy settings.

#1 piston - 100 PSI
#2 piston - 100 PSI
#3 piston - 70 PSI

I pulled the head off and there are some grooves in the cylinder walls.
I have attached pictures.

Now I have to decide what to do from here.
What is the major expense as far as parts for rebuild?
I imagine one needs new rings, pistons and the block bored.
Does one need to do anything with rods and bearings like in an automotive engine?
Does one need to grind the crankshaft on an outboard normally?
Things could get expensive if I have to do all of that.

Is she worth fixing?

I have this motor on a 14' runabout. It is a lot of fun.
Plenty of horsepower for the small boat.

What you do?

Thanks
Lynn

 

[pnwboat]

Re: 1991 70 HP Force Little or no spark

Sorry to see you in this situation. Not that difficult to rebuild. All of the crank and rod bearings are needle type roller bearings. Most shops cannot regrind the crank as the bearing journal surfaces are hardened. As long as the roller bearings and bearing journals are not discolored and blue from excessive heat, or pitted, no need to do anything. Run them as is. Most shops that I've dealt with charge $30 to $40 to bore a cylinder. The pistons themselves are a little pricey in my opinion. Around $80 to $110 each depending on whether you use cast or forged. Definitely worth fixing in my opinion, but the final decision is really up to you.

 

[Farmerbouy]

Re: 1991 70 HP Force Little or no spark

Pnwboat

Would be scared of this?
The guy told me the compression was between 120 and 125.

1993 Force 70HP Powerhead Complete | eBay

Would also give me a bunch of extra parts

I offered him $375.00
Think I am crazy?

Lynn

Lynn