Having spark problems with my new rebuild

[teslaman]

I've finished installing my rebuilt 73 115hp Johnson and tried to start it today. Needless to say, it didn't go so well.

The engine isn't getting any fire. We noticed metal shavings falling from underneath the flywheel. We took the flywheel off and found two loose bolts. In our hast over Christmas break to install the rebuild, we obviously neglected to inspect the flywheel for loose materials.

Anyway, I cleaned the metal, removed the bolts, and from visual inspection nothing appears to be broken (wires, coils,....including the staator and timing ring). We put it back together, still no spark. I noticed that when I remove a sparkplug and ground the electrode that a very weak spark appears.

What simple tests can I do to verify that the stator/timing ring still function properly? The metal shavings where from the flywheel and were a result of the loose bolts rubbing against the flywheel. The metal did not come from the magnet area, but from the top of the arch.

Before the old motor blew, the ignition seemed to be fine. When we took all of the ignition components off of the powerhead, we kept as much assembled as possible.

 

[JUSTINTIME]

Re: Having spark problems with my new rebuild

u can test the ohms in the stator, but volts is what u want
u have a manual

 

[teslaman]

Re: Having spark problems with my new rebuild

I do have an 73 evinrude manual. I didn't look hard to see what the voltage should be. I did measure the AC volts on across 5 & 6 (wiring terminal where rectifier is) and got about 8Vrms. I'm not sure what this means though, I was just looking for something that would give me an indication of life.

Now my battery was not fully charged, but it should have had at least 75%. If my batt was too low, is it possible that low rpms by the stator reduce the inducted voltage by that much?

Tomorrow morning I plan on working on it some more. The batt is charging as we speak. I want to try several tests so that I can pinpoint the problem.

 

[imported_john_l]

Re: Having spark problems with my new rebuild

I have never worked on a motor that old but when I took my 8 horse 1985 outboard to a dealer he had a metal ring that fit around the ignition pick-up and magneto to align them. you may not have them properly aligned if you took them off.

I have no Idea how to align them without the special tool.

 

[JUSTINTIME]

Re: Having spark problems with my new rebuild

test ohms first to see if u have a complete circuit
to test volts u need a dva
u need a fully charged battery also

 

[ezeke]

Re: Having spark problems with my new rebuild

Since the battery, rectifier, etc have nothing to do with the ignition system, it is important to get to what does. Take the plugs out, and crank to 300RPM and assure that you do or do not have spark under those conditions.

If you do not have spark at 300 RPM, disconnect the black and yellow wire at the power pack and try again.

BTW, you probably cannot hit 300RPM with anything but a fully charged battery.

And one other thing; make sure you have that flywheel torqued to 105 ft lb. Frisbees that heavy make formidable adversaries.

 

[teslaman]

Re: Having spark problems with my new rebuild

Thanks Ezeke,

We did remove the spark plugs and got a very weak spark.

As for the 300 rpm, it appears that my rpm guage went out on me...it doesnt regester anything. I noticed that it had stop working the last time I took the boat out (when the engine blew).

What is the black and yellow wire to? I'll have a fully charged batt tomorrow.

 

[ezeke]

Re: Having spark problems with my new rebuild

The black and yellow wire that runs to the power pack is the kill wire.

When you turn the ignition key to off it crosses the black ground "M" connection on the ignition to the black and yellow wire [2nd "M"] and prevents the power pack from firing.

If it shorts anywhere in the harness or at the control, you will not get spark.

I know that you have a service manual and that the specification pages say 250 RPM for starting, but unless
everything else is close to perfect, 300 RPM is a better target.

The unregulated rectifiers are really sensitive. If you accidently swap polarity on the battery, or disconnect while running, or have a loose connection on the battery, they are trashed.

If the rectifiers get too hot from any of these conditions and melt, the wiring inside of them can fuse and allow battery current to get under the flywheel. Then you have bigger problems.

If you have fire to the plugs, act on the idea that you need to get more RPM.

 

[teslaman]

Re: Having spark problems with my new rebuild

I tried it again today with a fully charged battery and still got a weak spark. I would like to check rpm, but don't know if 300 rpm is too little for my tach to pick up.

I went ahead and performed the checks listed in the manual for the sensor and charge coils.

Sensor Coil
Manual says 8.5+/-1 ohms between #2 & #4, #9 & #12
#2 & #4: I measured 11 ohms
#9 & #12: I measured 10 ohms
each sensor to ground showed an open loop

Charge coil
Manual says 910+/-75 ohms between #7 & # 8
I measured 690 ohms
Open loop from each terminal to ground

So the numbers are not in the exact range, but I'm not sure that they show a major problem. Do these numbers sound too far off? I want to measure rpm, is there an easy or relatively cheap way to do it for 300 rpm?

 

[teslaman]

Re: Having spark problems with my new rebuild

Another thing that I forgot to mention. The manual states that the charge coil outputs 300 Vrms, so I took my voltmeter across terminals #7 & #8 (without disconnecting them from the powerpack) and measured 100 Vrms.

Should I get 300 Vrms from this measurement if everything is working accordingly?

 

[teslaman]

Re: Having spark problems with my new rebuild

It fired!!!

The spark during starting is small but the motor does start. I'm beginning to think that this is an old problem and may have been the reason why the previous owner used either to start.

I'm taking it to a mechanic tomorrow to do link'n synch. I'm going to ask that he check the rpms during starting as well.

 

[tschamp20]

Re: Having spark problems with my new rebuild

you the MAN! we, well i knew you could do it. mine was testy at first. i think it had to be "primed" either way cool deal. must have updates. do share.

 

[teslaman]

Re: Having spark problems with my new rebuild

I took it to the mechanic yesterday for linkn'sync and to check the weak spark problem at start-up.

If everything goes well, I'll take some pics of the rebuild. Then I'll have before and after pics to share.

 

[ezeke]

Re: Having spark problems with my new rebuild

This might be of interest:

http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=17;gtid=1278596