87 115 ignition dead in number 5

archbuilder · Aug 16, 2010

I have been working on my 115 for a few weeks. At first I thought I had a carburetor issue, it would run good up to about 4000. So weekend before last I decided to go thru the carbs to see if that fixed it. Took her out last weekend, still had the same problem. I replaced the plugs right before the carbs, so tonight I thought duh, you might want to look at the plugs. The number 5 plug looks just like it did when it came out of the box. Needless to say I won't be making a living repairing outboards

#1 thru #4 all looked like they have been burning. #6 looks like it has been burning, but maybe a little weaker. Any ideas on the culprit? I first thought coil, but I know the switch box can create issues also. Any help would be appreciated. I'm also planning on calling CDI tomorrow to pick their brains.

sxmerc · Aug 16, 2010

Re: 87 115 ignition dead in number 5

What you really need to do is hook up a spark tester and find out if there is or isn't fire on all six.

Bob_VT · Aug 16, 2010

Re: 87 115 ignition dead in number 5

good old fashioned timing light will work great

sxmerc · Aug 17, 2010

Re: 87 115 ignition dead in number 5

Bob_VT said:
good old fashioned timing light will work great

...or a timing light.

archbuilder · Aug 17, 2010

Re: 87 115 ignition dead in number 5

It appears after tinkering with things tonight that all of the other cylinders are hitting as they should. I went ahead and bought a coil for 25$, figured it was worth a shot. The plug and wire are both good. I also spent some time with the wiring diagram in front of the motor, trying to wrap my mind around it and how it works. I still don't have all of it down but I have a better idea. I need to spend some more time on the switch boxes and their role. Regardless, its nice to learn about how it works so I can have that information for future reference. That doesn't mean that I'm not frustrated with it, just that I'm at least learning!

redfury · Aug 17, 2010

Re: 87 115 ignition dead in number 5

Learning is more valuable than whatever it is you are learning about. Fortunately for us, these forums help us learn at a lot slower pace ( to our pocketbooks that is ).

archbuilder · Aug 18, 2010

Re: 87 115 ignition dead in number 5

Ok this is getting frustrating. I pulled off the cover and replaced the coil on number 5. Good news is the coil now at least fires erratically on number 5, bad news is it does so on number 4 and 6 now. Any ideas? I pulled the rubber cover off of the old coil, and There was some cracking. Here are a couple of shots of it.

I also have a mystery part that came in the Sierra package. I could find no apparent use for this part and figured it was for a different model with the same coil. There were no instructions in the package and looking at sierra's web site didn't help.

Any suggestions on where to go from here?

sxmerc · Aug 19, 2010

Re: 87 115 ignition dead in number 5

The mystery part is not used in your application. This coil fits several motoros, but this part is not required on your motor. No fire or erratic fire on 4,5,6 would indicate a bad stator or switch box. There ar two switch boxes on your motor. One for three cylinders each. With a DVA test voltage to and from the switch box that drives numbers 4,5,6. No or low voltage going in indicates a bad stator, low or no voltage coming out indicates a bad switchbox. Hope this helps.

archbuilder · Aug 19, 2010

Re: 87 115 ignition dead in number 5

The meter need to read the peak of the voltage wave correct (not the RMS)? I have a meter that will do that, but I haven't figured out how to use it correctly! The instructions aren't exactly comprehensive. I'm going to call the manufacturer today to find out how to set it up to read the spike voltage. I notice that CDI recomends swapping the stator leads from one switch box to the other. If the problem moves, then its the stator. If it stays in the same place its the switch box. I think I will try that today to see what happens. One other question, do the crack on the coil indicate that it is damaged or is that normal?

archbuilder · Aug 19, 2010

Re: 87 115 ignition dead in number 5

Also I have heard you need to replace the switch boxes in pairs, is that correct?

Faztbullet · Aug 19, 2010

Re: 87 115 ignition dead in number 5

Also I have heard you need to replace the switch boxes in pairs, is that correct?

Only if bia's circuit is out of spec's. Disconnect white/black wire and check the bias circuit (white/black terminals) resistance to engine
ground. Readings should be approximately 15,000 ohms and check both packs...

archbuilder · Aug 19, 2010

Re: 87 115 ignition dead in number 5

Thanks for the info, CDI says it is in the switch box. They were surprised that I still had the original ones after 23 years. They also recommended that I ohm out the the stator just to make sure there aren't any issues there.

87 115 ignition dead in number 5

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