1993 70 hp no spark

[grouper sandwich]

Ive been chasing a supposed fuel issue for over a year now. Lord only knows how much I have spent on carb cleanIngs, replacing the entire fuel system from the fuel pump to the gas tank and everything in between and actually rebuilding the carbs. At this point I was positive I no longer have a fuel issue, yet it still bogged intermittently at around 3200 or so RPM. Other times it would jump up and 5700+ RPM was no problem. But it would never last. That brings me to this past Saturday and a trip to Cape San Blas. A sunrise fishing trip started out with a frisky engine with places to go and fish to catch. After a 15 minute run and a drift across the flats it was back to bogging. The run home started with bogging but quickly kicked into high a gear and a WOT run back to the harbor. We pulled the cowl and tested the spark at various RPM ranges and luckily were able to reproduce the high RPM bog which should erratic spark on the light gun. Fast forward to the afternoon where about 15 miles of running produced mostly good performance. We docked it, headed to cook some steaks and kissed it good night. The next morning it would not crank no matter what we tried. We put it on the trailer and brought home. This evening after work I did a compression check and the numbers were as they always have been, 115 across the board. However, the spark test on the light gun shows no spark. I suspect CDI but before I put any more money into it I need to know what else to test and how. Any help would be greatly appreciated.

[99yam40]

Yamaha service manual and with the proper peak reading volt meter or a DVA adapter with regular meter you can test the inputs and out puts of the CDI, charge and pulsar coils feed voltage into CDI without the proper voltage in you will not get out what is needed

ohm test coils with ohm meter,
make sure the kill safety switch lanyard is hooked up 1st though

[grouper sandwich]

Thanks, I'll check all of that. And yes, the lanyard was connected, that was the first thing I checked. I was hoping against hope that it was just my stupidity and not an actual problem. Foiled by reality yet once again!

I've got a manual. Not sure what a DVA is, but I'll research it and get one if needed. I might be able to borrow the needed metering equipment from our marina.

Test input and output of CDI for peak voltage?
Ohm test ignition coils?

Am I testing the charge and pulser coils also, or will the input to the CDI tell if they are good?

[99yam40]

Service manual should give all info and testing procedures.
Yes the out of charge and pulars go to CDI
They will have ohms specs also

Might test key switch to make sure it is not killing the spark along with kill switch just to be sure. Could be the wire is grounded also. see if you can locate the kill wire at CDI and disconnect to see if spark comes back

[grouper sandwich]

Update. OK, the no spark was a idiot moment on my part. The key switch lanyard was on, just not all the way. A little extra effort to properly install it and spark was back. I sat in the corner for an hour with my dunce cap on for that one.

However, the problem of intermittent performance still exists so I ran ohm tests on the charge coil, pulser coil and charge and pulser on the CDI. Results were as follows at 90* F this afternoon.

Charge coil: 198
Pulser:313

CDI Charger: Blue-ground 16
CDI Charger: Brown-ground 12

CDI Pulser: W/R-ground .5
CDI Pulser: W/B-ground .5

Everything is within spec except for the CDI side of the pulser. Those values should be 37.5-1000 for W/R and 28-175 for W/B. Am I reading this properly in that I likely have a bad CDI?

[grouper sandwich]

Any advice on what my readings could mean?

[boats.net]

For an intermitten problem those test wont help you much, when it runs ok it will test ok, will need to run at problem rpm and run output test with a analog peak reading voltmeter to see which component is bad.

[grouper sandwich]

For an intermitten problem those test wont help you much, when it runs ok it will test ok, will need to run at problem rpm and run output test with a analog peak reading voltmeter to see which component is bad.

But it DIDN'T test OK is the issue. In fact, the pulser side of the CDI shows basically zero resistance. I'm confused. Is that result meaningless?

[boats.net]

I would run voltage output test before replacing CDI as CDI resistance test are not very good test.

[grouper sandwich]

10-4. I've got a DVA adapter on order to do just that. Thanks.