1977 Evinrude 75hp DMM question

[crwsound]

Hello,

Took our boat out last Friday, and about 5 minutes from the boat ramp the engine suddenly died. No warning whatsoever. We were tooling along at about 3/4 throttle, then suddenly we were going nowhere. I tried a restart, including with the spare gas tank...it would crank, but not fire.

I suspected no spark, which was confirmed when we got it home. No spark on any of the three plugs (this is a 1977 Evinrude 75hp outboard). I think that the problem is the power pack, but I need some information from people who know more than I do. Here's what you should know.

1) I've got good engine ground from the power pack, zero resistance between terminal 12 on the pack and the engine body.

2) IT'S NOT THE KILL SWITCH. I disconnected the black w/ yellow wire from the power pack, terminal 6 on the pack, and I still get no spark.

3) I'm pretty sure it's not the ignition coils. I don't have any spark for any of them, plus I checked the sensor coil resistance with my DVM and they're all at 8 ohms, within spec.

4) I'm pretty sure it's not the Charge Coil. I did a resistance check and it's a little bit low for spec at 450 ohms, but not too far off (spec is 555-705). Plus...

5) I'm pretty sure it's not the Stator. I cranked the engine with the stator leads disconnected from the power pack and connected to my meter (Fluke 89 IV DMM). There was a very high initial surge and then it was steady at 145 volts (measuring AC volts). From what I've read elsewhere online, that seems to be about right. Plus, nothing looks bad up there. I've read about leaking sludge, and broken magnets, but everything looks fine under the flywheel.

6) That leaves me with the Power Pack, where I think the problem is. I put the DMM on terminals 1, 2, and 3 of the pack (one at a time), with the ignition coil wires removed, and I got 45 volts there when the engine cranked (referenced to ground). I was measuring AC volts again, and here's my question. I can find no information anywhere telling me if 45 volts are good, or if that's too low. I'm working with a repair manual that tells me to use the S-80 or M80 neon testers, and I know that those are obsolete and everyone uses meters now. Trouble is, I don't know what the meter should tell me when testing the power pack. So I'm hoping someone here can enlighten me.

One other fact that might be relevant. Our battery is about seven years old and will only hold a charge for a couple of days...we haven't gotten around to replacing it yet. We take the boat out every weekend, so on Friday I put a charger on the battery so that it's charged up for our weekend. We've done that about four times. I know a low battery can cause no spark, but once it's charged up it's been starting the boat fine, and we usually stop and start the engine when we're out on the water - usually four or five times. So I don't think the battery itself caused the problem, but I'm wondering if the recharging might have shortened the power packs life some, if the pack is indeed the problem. Yes I know, I need to get a new battery and go from there (it's on the "immediate buy" list), but I'm still hoping to get an answer to my previous voltage question.


Thanks very much,
Chris


ps. Gotta love boaters. The first boat that passed by as we were paddling our runabout back to the boat launch gave us a tow in. Probably saved us about a half hour.

 

[jtexas]

Re: 1977 Evinrude 75hp DMM question

Powerpack is your most likely suspect. output voltage should be at least 150V peak AC at cranking speed (you'll need a peak-reading meter or DVA for your DMM). See the troubleshooting guide at www.outboardignition.com

You didn't hurt anything by charging the battery. But, have you tested the charging system? Note that if the rectifier fails, the tachometer stops working (tach isn't harmed, it just gets its signal from the rectifier).

You have a 6-amp unregulated alternator, and charging voltage can get pretty high at WOT so you'll want a good marine battery that can handle it. I use Interstate deepcycles for cranking, last two both lasted over 5 years.

 

[Sixmark]

Re: 1977 Evinrude 75hp DMM question

4) I'm pretty sure it's not the Charge Coil. I did a resistance check and it's a little bit low for spec at 450 ohms, but not too far off (spec is 555-705). Plus...
QUOTE]

The acceptable range is a variance 150 Ohms, yours tested out at 155 Ohms below minimum acceptable level, that's not a little bit low it's excessively low, if you are lucky enough to get by with just a power pack I would be surprised.

That coil would be in my garbage can like it was moldy bread.

 

[crwsound]

Re: 1977 Evinrude 75hp DMM question

Hey Gentlemen, thanks for responding.

JTexas that's exactly the info I was looking for. I suspected that the power pack voltage out to the coils should be way higher than 45v, but I just couldn't confirm that info anywhere I looked. I have not specifically checked the charging system, yet. I wanted to solve the spark problem then I figured I'd take a look at that. I will say that the battery seems to be recharging when I run the engine, it just dies after a day or so once I put the boat back in the driveway.

And yep, I definitely will be replacing with another marine battery. The one in there now has a 5 year guarantee and it's been in there over 7 years, so I don't feel too bad about that.

Sixmark, thanks for your note. I feel sheepish correcting your math, but the difference between 450 ohms and 555 ohms is 105 ohms, not 155 ohms. So since you say that the acceptable range is a variance of 150 ohms, then I should still be okay, right? I mean, obviously it's under, but it's still within acceptable variance. I'm not excited to pull the flywheel to replace the coil, so I think I'll replace the power pack and see how everything runs.

Thanks again for your responses.

Chris

 

[F_R]

Re: 1977 Evinrude 75hp DMM question

The power pack output to the coils is a series of very fast DC pulses. You can't measure them with an ordinary meter, that's why you need a peak reading meter.

 

[jtexas]

Re: 1977 Evinrude 75hp DMM question

Allow me to interpret for 6mark... upper limit of 705 minus lower limit of 555 means they've allowed 150 ohms of tolerance, and.......math skills aside.... ...you've increased the acceptable range by 2/3.

Myself, like you I prefer to leave the flywheel be and can't speak from direct experience with this particular part.............

 

[Sixmark]

Re: 1977 Evinrude 75hp DMM question

Hey Gentlemen, thanks for responding.

JTexas that's exactly the info I was looking for. I suspected that the power pack voltage out to the coils should be way higher than 45v, but I just couldn't confirm that info anywhere I looked. I have not specifically checked the charging system, yet. I wanted to solve the spark problem then I figured I'd take a look at that. I will say that the battery seems to be recharging when I run the engine, it just dies after a day or so once I put the boat back in the driveway.

And yep, I definitely will be replacing with another marine battery. The one in there now has a 5 year guarantee and it's been in there over 7 years, so I don't feel too bad about that.

Sixmark, thanks for your note. I feel sheepish correcting your math, but the difference between 450 ohms and 555 ohms is 105 ohms, not 155 ohms. So since you say that the acceptable range is a variance of 150 ohms, then I should still be okay, right? I mean, obviously it's under, but it's still within acceptable variance. I'm not excited to pull the flywheel to replace the coil, so I think I'll replace the power pack and see how everything runs.

Thanks again for your responses.

Chris

Sometimes my fingers get carried away

Anyhow, the point I was making is that there is a total accepted variance range of 150 Ohms the bottom of it being 555, you are 105 Ohms below minimum

Therefore it is NOT within acceptable variance, it is well below.

 

[crwsound]

Re: 1977 Evinrude 75hp DMM question

Sometimes my fingers get carried away

Anyhow, the point I was making is that there is a total accepted variance range of 150 Ohms the bottom of it being 555, you are 105 Ohms below minimum

Therefore it is NOT within acceptable variance, it is well below.

Got it, that makes sense. Sorry I didn't understand what you were saying before Sixmark. Thanks also Jtexas for the clarification.

Well, when I picked up a power pack an hour ago the guy quoted me $175 for the stator/charge coil unit - I asked just in case I needed it. That's not going to happen this season after $130 for the power pack plus a new battery (the wife won't allow it), so here's hoping that my well-below-spec charge coil will still start and run the boat. If not, I'll pick up a new coil in the winter sometime.

However...

It was the power pack! I just put it in, and immediately had a good healthy spark. So I put the plugs back in and tried to start it. One thing I've always loved about this engine: despite it's age, as soon as you turn the key with a little bit of choke (when cold) it jumps to life. And that's exactly what happened. I had it on the hose for cooling and it ran strong, just like it always does.

I don't know how long my coil will continue to serve me, but I'll wait until it really goes bad and doesn't start the boat. We actually have a 15hp Johnson that used to live on this boat for a trolling motor, I'll put that back on for a get-home motor. Just in case.

I'll test the battery charging circuit before I go out this weekend. Thanks everybody, this worked just like I'd hoped: I didn't have information, and people told me what I needed to know to help troubleshoot my engine. I appreciate it.

Cheers,
Chris

 

[Sixmark]

Re: 1977 Evinrude 75hp DMM question

Good to hear you are running again, but as you said you would do, keep an eye on that coil. having the 15hp is a great idea.

 

[boobie]

Re: 1977 Evinrude 75hp DMM question

One thing you have to remember about measuring ohms. Depending on what the air temp is and weither your in the sun or not they can vary. Some times a fooler.

 

[crwsound]

Re: 1977 Evinrude 75hp DMM question

One thing you have to remember about measuring ohms. Depending on what the air temp is and weither your in the sun or not they can vary. Some times a fooler.

Thanks for the reminder, yes, I wondered if that might be an issue. Although the engine wasn't in the sun when I was doing those measurements, it was the hot time of the afternoon, and everything was pretty warm around here. Of course I know it's a lot warmer in some other parts of the country, I'm just in Seattle, but still we're in a small heatwave. Anyway, everything is currently working great, so I'll just keep my ears pealed for strange sounds while running and starting. Plus of course check the charging circuit.

Thanks,
Chris