1990 force 120hp coils help

[puffitu]

Hey all
Is it possible to bench test the blue ign coils? I have 4 in total: one black firing the #1 cyl then the rest are the blue coils. Im having a tough time bench testing the blue coils. And while were at it whats the easy way to test the pwr packs.
Thanks

 

[Jiggz]

Bench testing means removing the part from it's original location and bringing it over to a work bench to test it. I don't believe this can be done unless you have the proper equipment. However, you can do an in place testing but you will need a DVA adapter to measure the voltage output. This output voltage is a transient voltage that lasts in milliseconds, hence cannot be measured with regular DVM's.

Don't quote me on this but this is the voltage outputs that I can remember: All readings are between output wire and ground.
Coils - 15K ~ 22K volts
CD Packs - 180+ volts

 

[jerryjerry05]

outboardignitiondotcom has test procedures for everything but the coils??

The best way is to ground the plug leads and then get a spark tester.
Test all the cyl.
Then when one has spark? swap the coils around and see if they spark??
In all my years, I've only seen one bad coil.
The packs or the stator has usually been the problem.

The black coil is a later product.
Blue came OEM.

Like Jiggz said, you'll need a DVA or an adaptor to change your meter.
You can do the ohms test on the stator but not much after that.

DVA readings should always be taken with everything hooked up. 2. Check for broken wires and terminals, especially inside the terminals. 3. Check the flywheel for broken or loose magnets. 4. Disconnect the kill wires from the CD and connect a DC voltmeter between the kill wires and engine ground, turn the ignition switch on and off several times. If, at any time, you see voltage appearing on the meter, there is a problem in the harness or ignition switch. At NO TIME SHOULD YOU SEE BATTERY VOLTAGE ON A KILL CIRCUIT. 5. Visually inspect stator for burned or discolored areas. If found, replace the stator. Burned areas on the battery charge windings indicate a possible problem with the rectifier. IF NO FIRE ON ANY CYLINDER: 1. Disconnect the kill wire AT THE PACK. Check for broken or bare wires on the unit, stator and trigger. 2. Using the Fluke meter with the 511-9773 peak reading adapter, or CD-77 and 511-9770 piercing probes, measure DVA voltage of the stator between the output wire sets. With everything connected, readings should be approximately 180 volts or more. Resistance readings between the stator wire sets is from 680-800 ohms (CDI will read 300-400 ohms). 3. Disconnect the rectifier and retest. If the engine fires, replace the rectifier. NO FIRE OR INTERMITTENT ON ONE CYLINDER: 1. Check stator and trigger resistance, trigger wire sets read approximately 50 ohms between the wire sets (DVA .5V or more), OEM stator will read 680-800 ohms (DVA 180V or more) from blue to yellow. (CDI Stators will read 400-500 ohms). 2. Disconnect kill wire from one pack. If the dead cylinder starts firing, the problem is likely the blocking diode in the other pack. NO FIRE ON TWO CYLINDERS: If two cylinders from the same CD unit will not fire, the problem is usually in the stator. Test per above. ENGINE

 

[puffitu]

Thanks for the input gents.
Stator & trigger check out ok according to basic tests ive done. Im not getting fire from #1 coil which is a black one unlike the rest which are blue and working. Would a faulty rectifier produce the problem? im going to pick up an adapter so I can take some solid readings.
The problem started after I noticed an overcharging on the dash voltage gauge a day prior to the engine loosing significant power at WOT. Ive already found a pre enjoyed coil and charge pack on ebay for $180 including shipping but will wait until I know for sure that's what it is. something tells me the rectifier is bad

 

[Jiggz]

The best way to isolate the problem is by switching the suspected bad coil with a known working coil. If the problem follows then you know you have a bad coil. There's no reason to bang around anymore just replace the bad coil and you should be good to go.

 

[jerryjerry05]

They used 2 different rectifiers, a square and a rectangular.
The square hardly ever went bad.
The other was pretty reliable too.
Try swapping the coils.

The trigger leads are very thin and break easily.
The shrink wrap often hides a broken wire.
Try pulling the wire at the connector and see if it comes apart?
I replace all the connectors: SOP

Compression test?

 

[puffitu]

All...all connectors have been replaced, new fuel pump and all new fuel lines, carbs redone, checked reeds, new head gasket, redid water jacket cover gaskets, all new gages, batteries, starter, water pump, plugs, water separator, in line fuel filter, new switches, decarbed, propeller rehabbed, fuses, fixed the fuel vent, new fuel sending unit, fixed live well pump and bilge, replaced a lot of wiring, Link and synked carbs...the boat runs; just a bit sluggish; before this power failure it was doing 31mph ish@4200rpm ish. The thing that I noticed is that right before the power loss the voltage reg was at about 16v then next run it went down to 12 and stayed; thought the issue worked itself out but the very next run the power loss so idk.
things that I haven’t gotten to are timing check, dva diagnostics of stator, trigger, and coils accordingly, rectifier is pointing me in bad direction. I’m pretty mechanically inclined but when it comes to electronics I’m stumbling around abit. I welcome all suggestions as on what to check; I’ve already wore a path to and from the garage and boat lol
is it possible to check timing even if I’m down #1? I’ve noticed that the bracket which is used to advance the timing etc has been jb welded and painted so two things; one is that maybe the previous owner repaired it and sold it like that and the thing didn’t move or it was repaired after the thing broke and moved...
thank you all who gave their priceless advice

 

[puffitu]

So after reading a post about someone else’s tdc issues -here’s mine after checking with screwdriver in top cylinder.

 

[Jiggz]

Close but not really TDC aligned unless you did not check the #1 piston accurately. Just to be sure, try again and if the same results, you will have to pull the flywheel to verify the key is not sheared. If the key is not sheared, then you will need to align the stationary marker (because it was JB welded) with the flywheel. Note, the flywheel key does not hold the flywheel instead it's only there as a marker for TDC on #1 cylinder. What holds the flywheel in place is the pressure on the tapered shaft.

Lastly, there are two types of ignition system for the 90-120HP, Prestolite and Thunderbolt. Prestolite uses the cd modules and coils system, while the T-bolt uses a switchbox and coils. Which one do you have?

 

[puffitu]

Presto I’m pretty sure. I switched the #1(supsedly bad) cold on down with the #3(good)coil and now I’m not getting fire on either 1 or 3 cylinders so I’m thinking bad coil and bad pack. Man I hope the key didn’t sheer because that flywheel would be a bear to get off; that but looks beat up and rusted almost solid-
thoughts?

 

[Jiggz]

Yup, that's a Prestolite ignition system. If after switching #1 with #3 coils and you do not get sparks on both, then maybe you should try to put them back in their original position and check for sparks again. And then post which cylinder (s) is not having sparks.

 

[puffitu]

Will do Jiggz; thank you. It’ll be a couple of days before I can get back to it

 

[puffitu]

So I got a chance to mess with it today and after switching back to original locations for the coils; the same result of #1 black coil being bad. I had already gotten the pre enjoyed new coil and pack in the mail so I proceeded to do the switch. After the pack and coil instal and some dummy checks I fired it up and it started right up. Had to adjust idle a tiny bit but as of now it’s purring better than I’ve ever heard it.
Ive gotten a dva adapter also but no diagnostics yet

 

[puffitu]

Checked for spark and all are firing

 

[Jiggz]

Checked for spark and all are firing

Great. When you get a chance you might want to double check the timing just so to get rid of any doubts. Remember, when you switch parts, the purpose is to isolate the source of the problem. Meaning if the problem follows the switched parts, then that part is faulty. You did well, and enjoy the rest of the season, well at least in the Northwest!

 

[puffitu]

Thanks jiggs
i may sneak it out tmrw for a run and yes the timing is on my mind. All the best-