CDI High Speed Failure

[sludgeguy68]

Engine is an I6 1979 115 ADI ignition, full rebuild in 2018. I replaced both switch boxes, trigger and stator with CDI units. I also added a mercury voltage regulator + rectifier, and bypassed the old diamond shaped rectifier to stop battery overcharging.

It's been running great until today, when I suddenly lose spark on cyl #1 & 5 at high speed only.
Swapped coils on #1 and problem did not move.
Swapped red + blue with red-white and blue-white, problem moved to cyl #3

Went through CDI troubleshooting guide and everything is in spec except for resistance on the red wire at near zero - I'm assuming this points to a bad stator?

I haven't popped the flywheel yet to look for an obvious problem, but I'm pretty disappointed this only lasted 5 years, I had thought CDI made decent quality stuff.

 

[1960 Starflite]

Following, What rectifier/regulator did you use to reduce voltage? My 850 Merc is charging 17.5 volts, don't like it, shouldn't have installed a volt meter

 

[sludgeguy68]

I wish I kept the part number but I can't find it. I think I found it in an old thread, probably buried in this forum, where a guy installed it on an early 80s merc.

Search for 815279-2 and that's what it physically looks like, with the potted epoxy, 6-wires. The two red wires can be connected together.

 

[1960 Starflite]

Thank You. Found several "compatible" units. Where did you mount it?

 

[boscoe99]

The best quality stuff in the world have have an earlier than expected failure. On the other hand, cheap stuff can last far beyond its expected lifetime. Just the way that it goes.

 

[boscoe99]

How many charge coils in the model? If it uses low speed and high speed charge coils it might just be the high speed charge coil that has failed.

 

[dingbat]

I haven't popped the flywheel yet to look for an obvious problem, but I'm pretty disappointed this only lasted 5 years, I had thought CDI made decent quality stuff.

Playing Frankenstein with a charging systems is risky. Not much tolerance for miss matched components.

 

[sludgeguy68]

Thank You. Found several "compatible" units. Where did you mount it?

My motor has an unpainted aluminum flange on the starboard side under the starter, where luckily nothing was attached. I just bolted through it and it also acts as a heat sink.

I don't believe your 850 has this kind of roominess, so you might need to get creative...

Not my pic but you can see the plate under the starter here:

 

[sludgeguy68]

Playing Frankenstein with a charging systems is risky. Not much tolerance for miss matched components.

Yeah this did cross my mind, and I suppose I took a risk here, however the CDI troubleshooting guide specifically states that a rectifier-regulator should be installed to prevent overcharging the battery.

Since no specific replacement model was given, I suppose I assumed there was some leeway there. That part number I referenced above works from 2.5HP - 275HP, 1988-2005... I mean, wow what a range! I went out on a limb and assumed that there's not some magical thing happening under the hood here (unlike a switchbox, haha)

I mean if the wrong RR unit was gonna melt their stator, I would think there would be more caution around this statement from CDI? Maybe I'll try to give them a call tomorrow.

 

[sludgeguy68]

How many charge coils in the model? If it uses low speed and high speed charge coils it might just be the high speed charge coil that has failed.

Yes it has high and low, so yeah that's exactly my thinking. Just wanted to make sure the trigger & boxes didn't get damaged. Especially after pulling this flywheel off again.

 

[Faztbullet]

Sound more like a switchbox bias problem than a stator problem on the spark loss

 

[Dave1027]

Yeah this did cross my mind, and I suppose I took a risk here, however the CDI troubleshooting guide specifically states that a rectifier-regulator should be installed to prevent overcharging the battery.

My 88 100hp does not have a voltage regulator. Came that way from the factory. While running at any speed past idle the voltage climbs to almost 16 volts. My battery is a cheap Walmart brand that is over 8 years old and still going strong. That high charging voltage does not seem to be harming it.

 

[sludgeguy68]

Sound more like a switchbox bias problem than a stator problem on the spark loss

hmm... yeah I don't think I checked the resistance on the bias wire. Nor did I attempt spinning it up with this wire disconnected (I was worried about piston damage while doing this at higher RPM, as the banks could be out of sync, from what I understand). I think I'll investigate a bit more before throwing money at a new stator, thanks.

 

[sludgeguy68]

My 88 100hp does not have a voltage regulator. Came that way from the factory. While running at any speed past idle the voltage climbs to almost 16 volts. My battery is a cheap Walmart brand that is over 8 years old and still going strong. That high charging voltage does not seem to be harming it.

Yeah my battery was fine too, but then I put in a nice little stereo and class D amp, speakers, sub etc. etc. My voltmeter was pegged and the thought of burning all that stuff out was certainly making me sweat a little!

 

[sludgeguy68]

I tested everything again with a different meter using cranking speed instead of idle speed, and all seems to be more or less in spec according to the CDI sheet. Not sure why I was getting a weird resistance on the red wire originally.

There's no mention of testing the bias circuit, however I've read that I should have > 1V on the black-white wire at cranking speed, which I do at first, but it does drop half a volt white continuing to crank. Not sure if this is indicative of bad pack(s).

I popped off the flywheel and I don't see anything melting, dripping, binding etc.

Aside from throwing another stator at it, I'm not sure what else to do to.

 

[sludgeguy68]

Also if anyone is interested in the aftermarket voltage regulator, I found the old thread here: https://forums.iboats.com/threads/a...e-regulator-anyone-actually-done-this.458373/

 

[Faztbullet]

Doubt stator will fix it...

 

[sludgeguy68]

Doubt stator will fix it...

You were correct - I left the stator in place and instead replaced both switch boxes. I now have spark on all cyls over 3K RPM. The boxes were suspicously cheap but appear to be working for the moment. Thank you sir!

 

[Faztbullet]

Be careful on the cheap boxes from Amazon as they can damage your motor. Only use the OEM, Serria or Prufex