Yamaha 2000 C50TLRY CDI question

renegade15

Petty Officer 3rd Class
Joined
Mar 29, 2009
Messages
99
Motor is a Yamaha year 2000 2-stroke C50tlry. I got the CDI troubleshooting page from CDI Electronics site to measure all the voltages I reference below.

So set out on a fishing day and idling out of the marina, boat died...dead in the water. Cranks but would not restart. Luckily was able to pole back to the dock and get on the trailer, headed home to diagnose. Discovered I was getting no spark to any cylinder...checked the usual suspects (kill switch, good battery voltage, good spark plugs) and borrowed a DVA adapter for my multimeter and discovered my voltage in the brown stator wire was in the teens, when it should have been 125V...pointing me to the CDI. I bought a used CDI and hooked it up. Started right up...yaay...still not right though as it was only running on the top two cylinders. Tested all trigger/pulse coil to cdi connections and they tested out fine going to the CDI, but voltage was low from the CDI to the bottom coil, should have been atleast 125V and was 50.3V. The top two were about 190V.
SO the million dollar question, can anything but another bad CDI cause that drop to one coil when the voltages going into the CDI are fine? Is it possible there is something else on the motor that could have damaged the used CDI to affect only one cylinder?
I'm pretty sold on picking up one of the CDI Electronics aftermarket CDIs since they are fairly highly regarded and a couple hundred less $$$ than Yamaha OEM. But I don't want to hook up a brand new unit and risk damaging it if that is a possibility.
Thanks in Advance!
 

renegade15

Petty Officer 3rd Class
Joined
Mar 29, 2009
Messages
99
99 yam40, do you mean while cranking, and both with all the connections plugged in? Then with the triplex waterproof connectors unplugged? Then yes, the testing sheet that both my mechanic and the cdi troubleshooting pdf had details on both connected voltage and disconnected voltage. The 50.3V was with everything plugged in both before and after the CDI, but my sparkplug wires off since I did not want the motor to start. This make sense?
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
yes connected (loaded) and disconnected( unloaded)
Just curious if the ignition coil hooked up might bring down the voltage if bad

By the way if you do not give the voltage some where to jump to( spark tester hooked up or just ground the plug wires) the voltage can build up high enough to damage coils if it finds its own path inside coil or CDI from what I have read
 

renegade15

Petty Officer 3rd Class
Joined
Mar 29, 2009
Messages
99
I was actually cranking with a spark tester grounded to a head bolt for testing. I swapped the no spark coil with one of the good ones and still the lower voltage prevailed. Sound like CDI to you?
 

renegade15

Petty Officer 3rd Class
Joined
Mar 29, 2009
Messages
99
Uggg...I guess it's time to order up a unit. I guess it could be worse...I could have a FICHT! Teeheehee
 

renegade15

Petty Officer 3rd Class
Joined
Mar 29, 2009
Messages
99
Yeah, I thought maybe the cylinder 3 pulse coil could be bad possibly, and the cdi ok. But the voltage going into the cdi, both connected and disconnected to the three pin plug was in spec. 3.5V connected and 4.7-4.9V disconnected for each of the trigger wires.
 
Top