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1974 Johnson 70 HP - won't start

G

georgejohnson

New member
So I'm new to outboard engines, and new to boating for that matter. Bought an old 16' Peterborough for some fun on the ponds near my cabin. First day out and the boat didn't start....what a let down. Actually, it did start for a while, but everytime I put it in drive it died. After several attempts it enentually just wouldn't start at all. The guy I bought it from said it was just serviced (and I believe that to be true), and before I bought it, it ran fine, started first turn of the key. Not sure now if I have 2 problems (starting and shutting off in drive), or if the 2 problems are related. Anyway, first step is to get it running!!

What I haven't done yet......checked compression.....didn't have the compression tester with me at the cabin. I also haven't checked the rpm while cranking, it seems most suggest it needs to be over 250 rpm. I never had a tach with me, so that hasn't been checked yet either. It did seem to be cranking over at a pretty good pace though.

What I have done:

1. Checked for fuel delivery....good.
2. Replaced the plugs which were 2 years old according to previous owner.
3. Checked the resistance of the stator winding and timer base.....within spec.
4. Checked the primary and secondary resistance of all 3 coils....all within spec.
4. Checked the Power pack with a diode tester as described on CDI Electronics website. Numbers didn't quite agree...see below.

CDI values (bracketed values are the spec values posted by CDI electronics on their website)

coil terminals - terminals 1 to 3 - 0.644, 0.648, 0.640 (approx 0.500)
timer base - terminals 4 and 5 - 0.636, 0.644 (approx 0.500)
ignition switch terminal - terminal 6 - 1.060 (approx 1.525)
sensors 1 to 3 - terminals 8 to 10 - 0.815, 0.840, 0,784 (approx 0.550)
sensor ground - terminal 11 - 0.651 (approx 0.500)

So these numbers don't exactly agree, but is checking the power pack with a diode tester sufficient? I haven't seen many people suggest that this was a valid way to check it.

With regard to spark at the plugs. I first checked the old fashioned way, that is, all plugs out, and check for spark with the plug that was removed (after grounding it to engine). In all 3 cases I had spark.

Then I checked for spark with a homemade spark tester, all plugs IN, and had started with a gap of about 1/4"......no spark on any of the 3 coils. I reduced the gap to about 0.040 and spark reappeared. Apparently, I should have spark with a 7/16" gap?

At 1 point I had wondered if the flywheel key was sheared, but the mark on the flywheel seems to agree with the TDC timing mark on the flywheel.

Any suggestions? Is my Power pack the problem? Don't want to throw money away without having a good feeling that I have identified the problem.
 
johnnygjr said:
You have fuel and spark from what we have read, Check the compression next
Click to expand...

Thats my plan, won't get back to it until the weekend as I've left the boat at the cabin. Do you think that the spark is weak though? It's supposed to jump a 7/16" gap right?

Next time I go up I will have a tachometer, I guess the spark strength is related to the speed the engine turns over, so if it's turning slow...it won't go.

I'm also going to bring a dial indicator so I can precisely check TDC against the timing mark. Want to be sure that the flywheel key didn't shear. Used a screwdriver on top of the piston this weekend, and it's probably not accurate enough to detect a small shift in the flywheel.

I'll be bringing a compression gauge too. I kind of doubted it being a compression issue, just because the engine ran a few days before without a hitch. Not likely the compression went from "good enough to start", to "won't start at all", in just a few days of non-use? Either way, I'll be checking it, but it strikes me as being more likely an electrical issue. I think I've got a Fluke 87v at work which can be used as a DVA meter from what I have read. Anybody have any experience with using a Fluke as a DVA meter? Apparently there are 3 fluke models which will work as a DVA meter, and the 87V is one of them.
 
Engine must rotate at 200-300 rpms to usually start up. Make sure battery is fully charged before compression test & trying to start
 
johnnygjr said:
Engine must rotate at 200-300 rpms to usually start up. Make sure battery is fully charged before compression test & trying to start
Click to expand...

Thanks Johnny, question for you, and I'm thinking ahead here. If the engine was nearby I'd just go step by step, but given that I only get an opportunity to test things out on the weekend, I'm trying to be prepared. On to the question....

If the motor isn't turning at 200 - 300 rpm, and assuming all wiring connections are clean and tight, is it most likely a starting motor issue such as brushes or windings? I guess it could be something causing the outboard motor to bind up, but it's pretty easy to rotate the flywheel with the plugs out. I'd be delighted if the problem was simply a worn out starter, is that a common issue? I guess being an engine from 1974, anything is possible.

Appreciate your input
 
A weak starter would obviously crank slower, After charging battery was it at least 12.4-12.8 volts on battery posts and the same at starter& solenoid? Does battery pass a load test after being charged? Any idea on age of battery? battery can be tested at your local auto parts store usually for free, they want to sell you one ! Automotive type is recommended for most marine applications not maintenance free ones. A rebuild of your starter might be less expensive than oem rebuild or an aftermarket new one! If your mechanically inclined tackle it yourself. Any starter or alternator shop can do it.
 
johnnygjr said:
A weak starter would obviously crank slower, After charging battery was it at least 12.4-12.8 volts on battery posts and the same at starter& solenoid? Does battery pass a load test after being charged? Any idea on age of battery? battery can be tested at your local auto parts store usually for free, they want to sell you one ! Automotive type is recommended for most marine applications not maintenance free ones. A rebuild of your starter might be less expensive than oem rebuild or an aftermarket new one! If your mechanically inclined tackle it yourself. Any starter or alternator shop can do it.
Click to expand...

The battery is new actually, and was showing a full charge during my attempts to start. After I got the boat out of the water and back to the cabin, I topped it up with a charger.

Again, just trying to think ahead so that I can do as much as I can when I get to the cabin this Thursday.
 
I read your thread again for the fifth time today, Did you ever get the spark to jump 7/16", this should be done with "plugs out" cranking between 200-300 rpms Have you checked main wiring harness for bad,loose,corroded connections etc? Is kill switch working properly?
 
johnnygjr said:
I read your thread again for the fifth time today, Did you ever get the spark to jump 7/16", this should be done with "plugs out" cranking between 200-300 rpms Have you checked main wiring harness for bad,loose,corroded connections etc? Is kill switch working properly?
Click to expand...

Well that's a very useful tidbit. I thought the plug test was done with the plugs in!?!? That might explain why I couldn't get any spark without reducing the gap down to 0.030. I don't head back to the cabin until Thursday evening so I've got a list of things to test, including disconnecting the black/yellow wire from terminal 6 (the kill switch circuit).

I've got a tachometer, a timing light and enough tools packed up to pull the flywheel if some of these tests send me that way. I also have a service manual and various johnson outboard pages printed from the web.

Thanks again for helping me out with this. Being new to outboards, it's been a real learning experience.
 
You need a DVA adapter to measure the stator AC output to pack. If its low its stator problem if ok it capacitor in pack(replace pack)
 
Thanks for the input Faztbullet. I borrowed a multimeter from work today. It's a Fluke 87V, only one of a few multimeters which has a fast logging or capture ability. It's actually listed on the Fluke website as one of the meters "underutilized functions".

www.fluke.com/fluke/uses/comunidad/fluke-news-plus/articlecategories/dmms/under-used_functions

This meter has a fast response time of 250 microseconds, and captures min and max values while in this mode. In peak min/max mode it will show the voltage at the crest of a sinusoidal AC waveform. I just tested it on household AC power and it shows a peak of 169VAC (120 * 1.414). Most meters will only the show the RMS values of AC power (120V for household power). The drawback of these high end Fluke meters is that they're not cheap, the 87V is about $500.

Will post the results of the stator tests when I get it checked. Appreciate any other advice that you folks can give.
 
So here is the latest. Started back at square one cleaned all battery terminal terminal connections and charged batter. Cranked engine over and measured rpm as 380 using an optical tachometer. Engine speed while cranking is good.

Went back to my list and checked that piston 1 is at tdc as per mark on flywheel. Used a dial gauge and mark was smack on tdc. So flywheel key is good.

Checked resistance of powr back between terminals 8, 9, 10 to terminal 11. Apparently it should read 175 ohms. I measured 125, 144 and 101 ohms. Not as concerned that they didn't read 175, but I'm surprised that the 3 numbers vary quite a bit. Some of the other powerpack readings didn't agree either, but they matched each other better than these values.

Done 1 more test before darkness set in. Pulled off the rectifier and tested it. Most troubleshooting guides say to disconnect the rectifier and replace it if the engine now starts. I didn't even try to start the engine after removing the rectifier.....really ran out of tI'm to be working outside. I did check the rectifier with a multimeter once I hot inside. It failed the tests. It seems the diodes are toast.

Will try to start the engine in the morning. Hopefully the rectifier is the only issue and the engine starts up fine with the rectifier disconnected.
 
johnnygjr said:
Keep us posted,eager to hear outcome
Click to expand...

Well....not the immediate outcome I was hoping for. The engine didn't start withe the rectifier removed.

Checked the output from the stator:

When connected to power pack only 24v output
When disconnected from the power pack output was greater than 200 V

So the test is supposed to be done withe the stator connected to the powerpack. The resistance of the stator is within spec, about 600 ohms.

Question is, given this result is this a stator issue or a powerpack issue?

Checed the timer base output too. Was within spec, greater than 1 V.
 
So the CDI ELECTRONICS website describes this symptom as a power pack issue. The exact symptom being ...... low stator output when connected to powerpack and a normal stator output when disconnected from the power pack.

Does anybody have a different opinion?

I'm guessing that the failed rectifier took out the power pack. I've read that a failed rectifier can kill other components.

Picking up the parts and will have them installed later today.
 
Does anybody have a match? Still didn't start!!

I do have good spark now, jumping a 7/16 gap. I didn't hook up the black/yellow wire. I checked it and I was seeing 0.25 v on it. When I switched on the choke I would see 0.5 v on the wire. With the key off it was showing no voltage. I played it safe and left it disconnected. Shouldn't need it connected as near as I understand. Ignoring this issue for now.

So I'm not sure why it's not starting now. I had to walk away from it......too frustrated to work on it right now. I checked the timer base dva reading. It was way over 0.5 V. I'm baffled.
 
Updaye. ...all electrical problems seem to be gone. Spark is jumping a 7/16 gap. Got good output from timer base. Turning over at good speed.

Now I'm thinking I may have bad gas. Got to do a few checks this afternoon. The guy that I bought the boat from said the engine just burned half a tank from the fuel can that he gave me. I'm not conviced.
 
So I'm still picking at it. May have found an issue.

I marked tdc on the flywheel for each of the 3 cylinders. Number 1 of course is already shown and agreed with tdc as indicated on a dial indicator. So still no indI cation of a sheared key

Hooked up a timing light to catch the spark on cylinder 3. Used the timing light to see if the timing was right. Turns out that when piston 3 is at tdc the engine fires on cylinder 1.

When I had the timing light on cylinders 1 and 2, the engine fires on cylinder 2.

Doesn't exactly make sense but I'm going to switch sensor wires for cylinder 1 and 3 and see if the firing corrects.

Is it possible that the timer base is installed upside down?
 
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