1975 70HP killing power packs after shutoff...(fixed)

[dr1553]

Hi,

I have a 1975 70hp Johnson that is killing power packs. I have gone thru 3 so far. The motor starts and runs great until I shut it down.....then the pack is dead. Replace the pack and it fires right up again. Now the strange part. It doesnt kill packs running it in the driveway, the packs only die after it has been running for awile in the water. But it doesnt die while its running.....it runs great until I shut it down. So far it killed the original pack, a used OMC pack and on sunday it killed a bran new sierra pack 10 miles offshore. The motor ran great for the 30 minute trip out there and then when I tried to restart it after our first drift nothing....no spark at all.

This problem has my local OMC mechanic scratching his head too. I have replaced the ignition switch, checked the yellow/black kill wire for frays, and changed the ground wire on the pack and checked all the other ground wires I could find. They are all good.

Any thoughts? My mechanic wants me to replace the stator but I dont know. If the stator was bad would the thing run great until I turn it off? Seems like it would run bad and kill the pack while the engine was running.

 

[dr1553]

Re: 1975 70HP killing power packs after shutoff...

Re: 1975 70HP killing power packs after shutoff...

It seems like I read a thread here once that the rectifier could do this. I have searched and searched and cant find that post. I think the guy said that a bad rectifier can hold a small charge and when the motor is shut down it can send that charge to ground? Since the power pack shares a common ground with the rectifier that can do it. What has me confused it that it only kills packs when the motor is shutdown/dies after a good 20-30 minute run.

I cant keep throwing packs at this thing. I also cant afford to take it to the mechanic. Gotta get this figured out myself.

 

[F_R]

Re: 1975 70HP killing power packs after shutoff...

Re: 1975 70HP killing power packs after shutoff...

It seems like I read a thread here once that the rectifier could do this. I have searched and searched and cant find that post. I think the guy said that a bad rectifier can hold a small charge and when the motor is shut down it can send that charge to ground? Since the power pack shares a common ground with the rectifier that can do it. What has me confused it that it only kills packs when the motor is shutdown/dies after a good 20-30 minute run.

I cant keep throwing packs at this thing. I also cant afford to take it to the mechanic. Gotta get this figured out myself.

Whoever said that about a rectifier doesn't know how a rectifier works. They do not take or hold a charge. Besides, just because everything shares a common ground doesn't mean everything is on the same circuit. You should see how many circuits there are in a TV, all sharing a common "ground". In fact, the so-called "ground" can actually be the negative on one circuit and positive on another circuit, all at the same time.

I have no idea why turning the motor off should kill the pack. Never heard of such a thing. Seem like it should somehow be related to the ignition switch or wiring.

 

[dr1553]

Re: 1975 70HP killing power packs after shutoff...

Re: 1975 70HP killing power packs after shutoff...

Whoever said that about a rectifier doesn't know how a rectifier works. They do not take or hold a charge. Besides, just because everything shares a common ground doesn't mean everything is on the same circuit. You should see how many circuits there are in a TV, all sharing a common "ground". In fact, the so-called "ground" can actually be the negative on one circuit and positive on another circuit, all at the same time.

I have no idea why turning the motor off should kill the pack. Never heard of such a thing. Seem like it should somehow be related to the ignition switch or wiring.

Thats what I was thinking about the rectifier also but I wasnt ruling anything out.

Should have said before....after the 2 1/2 hour run home on the 15hp kicker I tried to get it started in the driveway. No spark. Put on a new ignition switch, still no spark. Put on another pack and it fired right up. If the ignition switch or the kill wire was the problem shouldnt it kill packs in the driveway when I shut the motor off also? It only kills packs after a good run in the water. The OMC mechanic is confused by that also. He thinks it might be the stator and wants to test run it on the water with a testing tool hooked up. But if I pay him for his time and it kills another pack while he is testing it then I should have just bought a new stator to begin with.

Could a bad battery somehow cause this problem? The battery I am using is a continental that I bought in June of 2000. I know its really old but I've never had problems with it starting the motor so I havent replaced it.

 

[F_R]

Re: 1975 70HP killing power packs after shutoff...

Re: 1975 70HP killing power packs after shutoff...

Thats what I was thinking about the rectifier also but I wasnt ruling anything out.

Should have said before....after the 2 1/2 hour run home on the 15hp kicker I tried to get it started in the driveway. No spark. Put on a new ignition switch, still no spark. Put on another pack and it fired right up. If the ignition switch or the kill wire was the problem shouldnt it kill packs in the driveway when I shut the motor off also? It only kills packs after a good run in the water. The OMC mechanic is confused by that also. He thinks it might be the stator and wants to test run it on the water with a testing tool hooked up. But if I pay him for his time and it kills another pack while he is testing it then I should have just bought a new stator to begin with.

Could a bad battery somehow cause this problem? The battery I am using is a continental that I bought in June of 2000. I know its really old but I've never had problems with it starting the motor so I havent replaced it.

The battery is in no way connected to the power pack at all. At least it isn't supposed to be. The ignition system generates it's own electricity (stator). There are other coils on the stator that charge the battery, but they are separate and islolated from the ignition.

 

[dr1553]

Re: 1975 70HP killing power packs after shutoff...

Re: 1975 70HP killing power packs after shutoff...

The battery is in no way connected to the power pack at all. At least it isn't supposed to be. The ignition system generates it's own electricity (stator). There are other coils on the stator that charge the battery, but they are separate and islolated from the ignition.

I guess I can go and run it and see what happens. I have replaced the ignition switch and checked the kill wire so it rules those out. If another pack goes bad I'll have to keep looking. Or I do have a spare parts motor with a stator on it. I could switch it over and then try it. But if the original stator isnt bad I hate to throw it away without knowing if it was the cause. It could have been the ignition switch that I already replaced.

 

[willamettejeff]

Re: 1975 70HP killing power packs after shutoff...

Re: 1975 70HP killing power packs after shutoff...

Would first check and clean up all ground points and connectors on the motor. Do you have a manual for the motor. It describes how to static test the stator, trigger coils, charging coils, ignition coils and rectifier, Without a manual and a digital volt meter your just shooting in the dark as you have already been doing at some expense.

It is my understanding that any positive voltage on the kill wire (blk/ylw) will kill the power pack. This happens sometimes from a bad ignition switch, but you've already replaced that. You could try disconnecting the kill wire from the power pack and check for voltage to ground on the wire. Then, leaving the wire disconnected and covering exposed ring terminal, attach another wire to the kill terminal of the new power pack such that you can touch it to a ground point on the motor to stop the motor and then, water test it again. If the problem does not return, then there is something wrong in your cabling to your controls that might only happen when the boat is bouncing along on the water and not when just parked in you driveway. In any event I would not risk another power pack unless I did the static tests on the ignition components first.

Hope this helps,

Jeff

 

[bktheking]

Re: 1975 70HP killing power packs after shutoff...

Re: 1975 70HP killing power packs after shutoff...

Check the ground going to pin 12. 4-5 7-11 go back to the stater and timer base, 1 2 3 go to the coils. 6 goes to the key switch.

From another site: A faulty charging system will blow a power pack

another site http://outboardparts.com/troubleshooting/printguide.htm

Engine continuously blows power packs: When an engine starts blowing power packs repeatedly, especially on the same cylinders, replace the ignition coils on those cylinders. The inductive kickback from a bad coil can destroy the packs, even if the coils check good with all known tests. A stator that test good can also be sending spike voltages to the packs causing them to fail repeatedly.

 

[dr1553]

Re: 1975 70HP killing power packs after shutoff...

Re: 1975 70HP killing power packs after shutoff...

Would first check and clean up all ground points and connectors on the motor. Do you have a manual for the motor. It describes how to static test the stator, trigger coils, charging coils, ignition coils and rectifier, Without a manual and a digital volt meter your just shooting in the dark as you have already been doing at some expense.

It is my understanding that any positive voltage on the kill wire (blk/ylw) will kill the power pack. This happens sometimes from a bad ignition switch, but you've already replaced that. You could try disconnecting the kill wire from the power pack and check for voltage to ground on the wire. Then, leaving the wire disconnected and covering exposed ring terminal, attach another wire to the kill terminal of the new power pack such that you can touch it to a ground point on the motor to stop the motor and then, water test it again. If the problem does not return, then there is something wrong in your cabling to your controls that might only happen when the boat is bouncing along on the water and not when just parked in you driveway. In any event I would not risk another power pack unless I did the static tests on the ignition components first.

Hope this helps,

Jeff

I do have the original service manual. I will do the static tests that can be done with an analog multimeter tomorrow. When the first pack blew it was the original, the second was an old used one. It wasnt until this new sierra one blew that I got worried. Thats why it didnt bother me to throw on another pack without testing the other components first. Now I know there is a bigger problem than just old packs.

It may be time for me to go ahead and just replace the coils, stator, trigger and rectifier. That way all the bases are covered. I use this boat offshore and I dont want to be broke down out there again.

 

[dr1553]

Re: 1975 70HP killing power packs after shutoff...

Re: 1975 70HP killing power packs after shutoff...

Check the ground going to pin 12. 4-5 7-11 go back to the stater and timer base, 1 2 3 go to the coils. 6 goes to the key switch.

From another site: A faulty charging system will blow a power pack

another site http://outboardparts.com/troubleshooting/printguide.htm

Engine continuously blows power packs: When an engine starts blowing power packs repeatedly, especially on the same cylinders, replace the ignition coils on those cylinders. The inductive kickback from a bad coil can destroy the packs, even if the coils check good with all known tests. A stator that test good can also be sending spike voltages to the packs causing them to fail repeatedly.

Do you have more details on the faulty charging system blowing a power pack?

My coils are original. I had wondered if a bad coil could kill the pack but an OMC mechanic said no. Mine have the typical cracking but I painted the cracks with finger nail polish as I have read to do.

 

[bktheking]

Re: 1975 70HP killing power packs after shutoff...

Re: 1975 70HP killing power packs after shutoff...

Replace cracked coils. No, the site just listed the stator or coils causing the problem, which makes sense, the wires from the powerpack for to both components, just the task now of figuring out what is what. If this thing is offshore alot, as you said, replace the coils and stator.

 

[dr1553]

Re: 1975 70HP killing power packs after shutoff...

Re: 1975 70HP killing power packs after shutoff...

I static tested the stator windings, charge coils, sensor coils, ignition coils and rectifier per the manual. The rectifier is bad but everything else tested ok. Of course these tests dont tell you what is happening when the motor is running.

I was looking at the paper that came with the sierra power pack that my motor just toasted and it says to check for a shorted rectifier. So why if the rectifier has nothing to do with the power pack did sierra mention it? Strange.

I'm going to replace the coils and rectifier and see if that fixes the problem. If not is the CDI stator a good product? It can be had new for half the price of the OMC one.

 

[dr1553]

Re: 1975 70HP killing power packs after shutoff...

Re: 1975 70HP killing power packs after shutoff...

Today I got the new coils and rectifier put on. I also ran a new fuel line and rebuilt the carbs...no black stuff in the carbs so I got the old line out before it started melting. It was very soft however.

So since it killed the last pack it has a new ignition switch, new pack, new coils and new rectifier.

I have 15volts at the battery while at idle in the driveway now! I dont think the rectifier has worked in the 10 years I have owned the motor.

It ran great in the driveway, it idles better than it was before the new parts. I shut off and restarted it 4 times to make sure the pack was still good. Tomorrow I'm going to put it in the water and see how it goes.

I'll post the results.....keep your fingers crossed for me!

 

[jonesg]

Re: 1975 70HP killing power packs after shutoff...

Re: 1975 70HP killing power packs after shutoff...

I say you are getting voltage in the black/yellow kill wire when throttle is opened to full, something is shorting out in the controller.

Test my suspicion, disconnect the PP.
Turn ignition on and operate the throttle thru its range as if you were on the water and monitor the kill wire with a meter whilst doing this.
At some point I think you will see a voltage spike, thats all it takes.
Doesn;t have to be a big v spike.
Any voltage in the kill wire kills the PP instantly.

It doesn't happen in the driveway because you don't open the throttle to WOT.

Whilst it "could be" the coils I don't think it would run very well and you say it runs fine til it dies.

BTW, I would open one of those PP's up and see if you can fix it.
Look for a dead diode allowing the PP to short to ground.
As long as its running its fine, but it will not allow start up again as the circuit collapses. I'm guessing, but its as good a guess as any.

 

[dr1553]

Re: 1975 70HP killing power packs after shutoff...

Re: 1975 70HP killing power packs after shutoff...

I say you are getting voltage in the black/yellow kill wire when throttle is opened to full, something is shorting out in the controller.

Test my suspicion, disconnect the PP.
Turn ignition on and operate the throttle thru its range as if you were on the water and monitor the kill wire with a meter whilst doing this.
At some point I think you will see a voltage spike, thats all it takes.
Doesn;t have to be a big v spike.
Any voltage in the kill wire kills the PP instantly.

It doesn't happen in the driveway because you don't open the throttle to WOT.

Whilst it "could be" the coils I don't think it would run very well and you say it runs fine til it dies.

BTW, I would open one of those PP's up and see if you can fix it.
Look for a dead diode allowing the PP to short to ground.
As long as its running its fine, but it will not allow start up again as the circuit collapses. I'm guessing, but its as good a guess as any.

I can leave the kill wire disconnected from the pack and go run it in the water. I can let a buddy drive and I can monitor that wire while we are going. If another pack dies while the kill wire is disconnected then it has to be the stator or timing base.....thats all thats left. If I dont see a spike on the kill wire and the pack survives killing the motor with choke then I will reconnect the kill wire and try again. If it dies then it has to be the wire....if it survives then It had to be the ignition switch, coils, or rectifier. I'll get it figured out tomorrow.

How can I open one of those packs? The board is bedded in that resin stuff. It would be nice if I could fix them. A few spares would be nice to have.

 

[jonesg]

Re: 1975 70HP killing power packs after shutoff...

Re: 1975 70HP killing power packs after shutoff...

I can leave the kill wire disconnected from the pack and go run it in the water. I can let a buddy drive and I can monitor that wire while we are going. If another pack dies while the kill wire is disconnected then it has to be the stator or timing base.....thats all thats left. If I dont see a spike on the kill wire and the pack survives killing the motor with choke then I will reconnect the kill wire and try again. If it dies then it has to be the wire....if it survives then It had to be the ignition switch, coils, or rectifier. I'll get it figured out tomorrow.

How can I open one of those packs? The board is bedded in that resin stuff. It would be nice if I could fix them. A few spares would be nice to have.

Sounds like a plan.
Try a heatgun on the potting material in the PP,
what have you got to lose, its already shot
Try heating the plastic case and pulling the potting material out.
Someone else on here did say they got one apart and found blown components.

 

[dr1553]

Re: 1975 70HP killing power packs after shutoff...

Re: 1975 70HP killing power packs after shutoff...

Ok...I think I got it fixed. I took it out today and ran it for about an hour and the pack survived. I ran it with the kill wire disconnected and never saw any voltage on it so I hooked it back up and ran it some more. I shut it off and restarted it probably 10 times and no problems restarting. It is a little rough at idle so I need to get that figured out. I just rebuilt the carbs so its not that. I think after putting new coils, new pack and pulling the flywheel to inspect the stator that I need to check the timing. But the motor sounds great wide open and its not killing packs so I'm happy!

Thanks for all the responses and help!

BTW...there was a guy at the ramp with a 70's maybe 80's 115hp Johnson. Said he couldnt figure out why it was running so rough....it was I heard it. I asked him if he had replaced his fuel lines and he got that "ohhh!!!" look on his face. Ethanol poisoning I bet.

jonesg.....I will try the heat gun idea.....your right....whats it gonna hurt?

 

[willamettejeff]

Re: 1975 70HP killing power packs after shutoff...(fixed)

Glad to hear you fixed your problem dr1553 and thanks for providing the feedback. As I also have a 70hp Johnson from the seventies I was very curious about what was causing yours to blow powerpacks. Thanks again for letting us know you got it fixed.

-- Jeff

 

[dr1553]

Re: 1975 70HP killing power packs after shutoff...(fixed)

Glad to hear you fixed your problem dr1553 and thanks for providing the feedback. As I also have a 70hp Johnson from the seventies I was very curious about what was causing yours to blow powerpacks. Thanks again for letting us know you got it fixed.

-- Jeff

Jeff,

Wish I could say exactly what was killing the packs. It was either the ignition switch, coils, or rectifier. Those are the parts I replaced. That or I got three bad packs in a row....I doubt that.

I can guess what it was. I dont think it was the ign. switch because when the last pack died I never shut off the switch...the motor died at half throttle. I would say it was the rectifier but everyone I have asked says thats impossible. So that leaves the coils. They were cracked up so I know they had to be leaking some voltage.

If you have a 70's motor and your coils are cracked up I say replace them. Also check those ground wires. I ran all new grounds a few years back because mine were looking bad. These motors are now 30+ yrs old. Long time for wiring and electronics that sit outside and get exposed to salt water like mine.

David

 

[willamettejeff]

Re: 1975 70HP killing power packs after shutoff...(fixed)

If you have a 70's motor and your coils are cracked up I say replace them. Also check those ground wires. I ran all new grounds a few years back because mine were looking bad. These motors are now 30+ yrs old. Long time for wiring and electronics that sit outside and get exposed to salt water like mine.

David

I did something a little more drastic, in that I put the entire ignition system from a 1989 60hp Evinrude I got on Ebay onto my 1978 70hp Johnson. This included the bracket the powerpack, coils, and the tilt and trim relays are mounted on. Turns out the my motor had the bosses and pre-threaded mounting holes for the bracket. Just had to cut off some of the bosses the the original bracket mounted to.

Have only run it on muffs so far, as I'm just finishing renovations on my boat, but seems to run much better and has much greater spark. Boat is finally ready to put everything back on, so will get a chance to try it soon. Have saved all of the original components just in case, but don't think I'm going to need them.

-- Jeff