Powerpack Swap to GM Ignition is it possible?

[Vigilante]

I've just bought a '73 - '77 85 evin' with no spark and am suspect of that power pack. Being the GM guy that I am I'm considering connecting 4 GM ignition modules in place of the PP since I have a few laying around. I know the crap out of a chevrolet but 2 cycle engines are very forein to me. I bought the '56-'72 shop manuel but didn't find a good match. I,m thinkin' '73-'77 'cause the picture matched my power pack. I think that the Evin's coil is switched by +12 volts where GM switches the ground. If the PP is truely just a points type switch theoreticly it'll work.......I think!?! (I was able to get a Datsun fuel injection system working well on my jaguar) but those are cars. I't seems that boat engineers think differently that automotive engineers. Any input apreciated good or bad

 

[gatorred]

Re: Powerpack Swap to GM Ignition is it possible?

check see if point's under flywheel my 9.9 had point's in it but no powerpack on it coil's looked like powerpack one's

 

[Vigilante]

Re: Powerpack Swap to GM Ignition is it possible?

My motor has two sensors similar to electronic ignition doesn't really make sense with four coils but the;re clearly marked on the power pack. 9.9 is one cylinder, Right? That would be a relativly logical swap to a GM ignition module.....Me thinks.

 

[ezeke]

Re: Powerpack Swap to GM Ignition is it possible?

Standard automotive parts won't work on the 73-77 85HP. It is a capacitor discharge ignition.<br /><br />Try finding the model number. Its on a 1"X3" plate on the left (port) side transom bracket.<br />or failing that, on a round welch plug on the top of the port bank of cylinders.<br /><br />You can get a better idea of the electronics from the Rapair Troubleshooting Guide. It is long so be patient on the download. CDI Troubleshooting Guide

 

[Vigilante]

Re: Powerpack Swap to GM Ignition is it possible?

Too dark to see model #. Thank you very much for the pdf that certainly helps. Your right about using the stator to fire the coils 150 volts would more that likly blow the GM 13.8 volts it was designed for, However, If the entire ignition reusing only the sensors was replaced coils and all just as a "see if I can do it" project what problem do you think I'll incur. It is an awful amount of work to bypass a $100.00 part but It's more the priciple of accomplishment, or some bi-polar mental imbalence.

 

[rodbolt]

Re: Powerpack Swap to GM Ignition is it possible?

those arent really sensors on the CD ign system, the charge coils,part of the stator assy, provide an AC voltage to the CD unit where its stored in a capacitor, the pulser coils develop a smaller AC control voltage used to trigger an SCR gate that allows the cap to discharge into the coiul primary winding, maybe thats why they call it a Capacitor Discharge system. some of the 72 and older V4 systems used a battery CD system with crank position sensors as triggers but the sensors did the same thing, as the inner crank hub mags pass the sensor it generates a sine wave that the CD amplifier used as a trigger.<br /> nice thing about electrons is they dont care, nice thing about that motor it does not either. as long as the spark occurs at the correct time in relation to piston travel the source of the spark is irrelevent.

 

[alden135]

Re: Powerpack Swap to GM Ignition is it possible?

Originally posted by Vigilante:<br /> It's more the priciple of accomplishment, or some bi-polar mental imbalence.

You're going to like it here at iboats.

 

[Vigilante]

Re: Powerpack Swap to GM Ignition is it possible?

All this information is very helpful and I am certainly appreciative of your responses. It looks like I'll need a completly re-engineer the ignition system for sucess here. I'm a big fan of those MSD (multiple spark discharge)Ignition sytems. These ignition modules fire the spark plug several times during the combustion cycle. I know if I can get the GM ignition module to work I can get the MSD ignition to work. I did have a question about the timing. If I understand this correctly, does the engine's RPM directly relate to the timing advance postion more so than the throttle body position (if there is a throttle body I guess I never checked)? If so does this cable need adjusted to the amount of boat weight and can you sqeeze more RPM's with a tweek here.<br /> Can you tell I'm one of those A-hole hot rodders from Ohio.

 

[rodbolt]

Re: Powerpack Swap to GM Ignition is it possible?

ign timing on that engine is controled by the trigger plate under the stator assy, its very critical. most two strokes wear plugs very rapidly with MSD.<br /> miss the timing much either way and you will see what detonation/piston erosion looks like.<br /> that motor has no TPS.

 

[McGR]

Re: Powerpack Swap to GM Ignition is it possible?

I wouldn't say you couldn't do it. But it would be quite a feat of engineering. I've daydreamed about similar thoughts myself over the years.<br /><br />Basically you'd have to scrap the OMC system and start from scratch. The original design used two pickups/sensors that were shared by two cylinders each. When polarized one way by a passing magnet in the flywheel, the sensor would fire a particular cylinder. The same sensor would also be polarized in the opposite direction by a second magnet in the flywheel to fire another cylinder... In short these sensors would never interface with a GM module (at least not without a lot of electronic help). <br /><br />So, here’s what I think you’d have to do:<br />- devise and properly time four GM HEI compatible sensors and poles on the flywheel. (no small task)<br />- change out the four CD coils to four standard automotive 12V coils. (probably could be done)<br />- Use 4 HEI modules, as you will no longer have a distributor. So, you’ll have to dedicate one to each sensor/coil/cylinder. ($ start adding up here)<br /><br />All in all, when you consider the effort, it’s cheaper and easier to just fix the relatively reliable OEM system. However, if you were absolutely determined and had enough know how and were purely doing it for experimental reasons and had time, money and patience... I think you could make it fly.

 

[Vigilante]

Re: Powerpack Swap to GM Ignition is it possible?

Well stated McGR. In all acuallity I'm just mad at this design because I don't understand it. I'm the type that has to know exactly how it works and if I don't modify at least one part it won't feel like it belongs to me.<br /> Is there a scamatic on the inner workings of the power pack or is that top secret OMC knowledge? I can almost think of a series of capacitors and diodes that would mimic a PP (almost). I may be the only fool on the planet that would want to fabricate this item (at least thats what the wife and kids belive).<br /> Also I can't thank you enough ezeke for the troubleshooting PDF. The comments from everybody may turn me into a boat person yet

 

[McGR]

Re: Powerpack Swap to GM Ignition is it possible?

I'm similar to you in that I enjoy performing some unconventional tinkering from time to time. The power pack is basically a capacitor to store the charge from the charge coil, four SCRs to dump the contents of the cap into the coils when required and a handful of diodes, small caps and resistors take care of rectification etc. Overall, the parts count is fairly low and its a quite simple circuit. In fact, I actually decapsulated the one on my '76 85hp and repaired it a few years ago. I bought a new one anyway, and just keep this onboard as a backup. There is a schematic in the factory manual. If I remember this evening when I'm home, I'll scan and post a copy.

 

[Vigilante]

Re: Powerpack Swap to GM Ignition is it possible?

That is super cool of you McGR I'll be looking for that. However. I checked the stator for continuity and got 2 Ohms and the rectifier reads 0 Ohms from brown to black and brown to red both directions. Very discouraging. I stopped checking parts at this point. I'm pretty sure I've got a rectifier but how would you go about re-wrapping the stator coils.....Just kidding. I REALLY don't have that kinda time. Looks like I'm taking a trip to the boat store to get ripped off again.<br /> They say a fool and his money are soon parted and as God as my wittness I am that fool otherwise I wouldn't have a boat.

 

[McGR]

Re: Powerpack Swap to GM Ignition is it possible?

Here's a copy of the powerpack diagram. I hope this helps...<br /><br />

 

[rodbolt]

Re: Powerpack Swap to GM Ignition is it possible?

can I ask why your checking the rectifier?<br /> ya should be checking the charge coils for correct resistance and peak output voltage and the sensors for the same, the rectifier really has nothing to do with ign on that system.<br /> best I remember the rectifier leads were yellow.<br /> what does your service manual indicate for charge coil,NOT battery chargeing, resistance and trigger coil(sensor) resistance?<br />its an incredibly simple system.<br /> it really really does not get much simpler than the PPK-4 system.<br /> however it does require a basic understanding of AC current generation,AC current rectification and storage and SCR triggering.<br />had a big argument in a yamaha electrical course about how the SCR is turned on and off,<br /> seems the instructor did not know how to turn one off.<br />the ign system can be broken into 2 basic parts, ign producing components,charge coil,pack and trigger coils and ign coils and ign controlling components, timer base,stop switch and anything else that modifies the ign system.<br /> the producing components are simple,pass a magnet(flywheel) around a coil and it produces AC. send that AC through a rectifier and its DC. store the DC in a capacitor.<br /> now we need to discharge that cap through the primary coil windings.<br /> by inserting an SCR in the primary coil winding circuit we now have an electronic switch.<br /> an SCR is a voltage controlled current controlling device.<br /> its off until triggered by a gate voltage,normally less than 1V, and on until it current drops below its cut off voltage, then its off until the next gate signal.<br /> the gate signals are provided by the sensor(trigger) coils.<br /> you have to watch some of the service manual schematics as usually the dont show all the components.<br /> most the trigger signals are modified from a sign wave through clipper and clamper circuits.<br />usually the input voltage is regulated as the faster the flywheel spins the higher the voltage and eventually it will burn out a component.<br /> thats the function of some of the Zener diodes in the above circuit.<br /> the magnets on the outer flywheel rim produce the AC for ign charge coil circuits and the battery chageing circuits independantly of each other. the inner hub magnets produce the ac signal for the SCR's gate signal.<br /> if you can uppot it without destroying it you will usually find a bad solder joint or a faulty capacitor.

 

[Vigilante]

Re: Powerpack Swap to GM Ignition is it possible?

To answer your question Rod I checked the regulator 'cause it was there and seemed easy to check. I probebly should check output voltage before I purchase any parts. As far as the wire colors they were probly at one time yellow but when I looked at 'em they weren't. I like to remember the important stuff and pull every thing else out of context. My Service manuel would be compliments of Mr. McGR posted earlier the service manuel I bought refers to the ignition system as something required for the engine to run. Theoretically wouldn't the SRC gates preform the same fuction as Oooh saaay the GM Ignition module? Or am I siding with your Yamaha instructor. I don't mean to argue with you I'm sure your knowledge in this topic far exceeds mine I'm just not seeing your side of the arguement.<br /> Incidently on the PPk diagram is shows a ground above #6 above CD cap is that the black yellow wire or should that be shown on the other end of the regulator. My 15 year old daughter called me a dork for being interested in this but I look forward to this all day.

 

[Vigilante]

Re: Powerpack Swap to GM Ignition is it possible?

and how is that ZENER diode different from the reguler one

 

[Vigilante]

Re: Powerpack Swap to GM Ignition is it possible?

My Inner hub coil is craked and oozing. Can the SRC gates be hotwired from the ignition wire at 12 volts and omit the Black/Yellow wire?

 

[Paul Moir]

Re: Powerpack Swap to GM Ignition is it possible?

The big difference is that the capacitor (CD CAP) is charged up to a few hundred volts rather than the 12 that's dropped over an automotive coil. That allows for much smaller ignition coils. The pulse is also quite a bit shorter than your typical automotive primary.<br />The capacitor needs to be designed to put up with these sudden, large discharges. I think that's one of the more common faults with powerpacks, but it's just a guess.<br /><br />Zener diodes break down in the opposite direction at a particular voltage. Like a regular diode it conducts in one direction (droping a volt or so depending on the current it's conducting) but instead of blocking in the other direction, it only blocks to a point. Usually somewhere between 3 and 30v it suddenly turns into a conductor. Makes for a great protection device: if the voltage gets over say 15v, dump it to ground.<br /><br />Iboats memeber nordy reverse engineered his '90s powerpack and posted the schematic here. It's not a whole lot more developed then that one. It has some basic protection and a rev limiter, but not much more.

 

[rodbolt]

Re: Powerpack Swap to GM Ignition is it possible?

vigilante<br /> its all important stuff and all must be remembered at the same time as many things are happening all at once just as in the HEI and Delco EST systems whether its also EFI or not.<br />no you cannot hit the SCR's in the ppk4 system with 12V, they will instantly fry.<br /> the charge coils typically send 150plusV to the capacitor in the CDI unit where the AC is rectified and stored in the capacitor.<br /> the output of the cap is through the coil primay to ground. remember the cap is at a large electrical potential difference to ground. the SCR is an electrical on/off switch between the cap and ground.<br />when we use a small gate(trigger) signal from the sensor the SCR turns "on" and current flows from the cap through the coil primary to ground, the current flow in the coil primary builds a magnetic field.<br /> the SCR will turn"off" when current flow reduces to the SCR's designed turn off value. when current quits flowing the resultant collapsing magnetic field will induce a rather large voltage with little current in the secondary windings of the ign coil. now we have an incredible potential (voltage) difference that wants to be equal. so it finds the easiest path to ground. if all is well this path is an arc acrossed the plug gap, if all is not it arcs someplace else.<br /> it works identical to a point system only the current and switching methods are different, the results are the same.<br />over the years outboards have used magnetos,battery points, battery CDI systems were the 12v was amplified, altenator driven CDI systems(your ppk4) and transistor controled ign systems(TCI). all use the same mutual inductance principles that a current flowing through a coil creates a magnetic field and a collapsing field will induce a voltage in a coil only the currnt source and switching on/off methods have changed.<br /> like I say, trons is trons regardless of where on planet eath the system was made, they operate in a narrowly defined band of paremeters. <br />what GM systems are you familiar with ?