Yamaha won't shut off

[Short Bass]

My son has a 1987 model Yamaha 175. He recently replaced the oil tank and ever since the engine won't shut off. It runs great but pulling the kill switch, turning the ignition switch off and even replacing the ignition switch with a new one won't shut the engine down. Any help would be greatly appreciated.

[yam911]

The motor is stopped by applying a ground to the CDI and ignition control unit. Via a white wire.

Ground goes from the motor up to the key switch/kill switch via a black wire and then back to the motor via the white wire. If the ground does not make it to the key switch/kill switch or back to the motor then the motor will not stop running.

Unlikely but it could be either the ignition control unit or the CDI.

Gonna take some trouble shooting.

I would first disconnect the ten pin connector at the front of the motor. Inspect for any corrosion. Reconnect the connector. Start the motor. See if it now stops when the key is turned off. If so, well and good. You just fixed a lack of connectivity problem.

If not, stop the motor however you have been stopping it. Then start the motor again. Disconnect the connector again. Jumper the white wire terminal on the motor side ten pin connector to a good ground source. See if the motor stops.
zjump.jpg

[Rennerjd]

Hi, yam911 I’m short bass’s son. I have replaced the whole control box, cdi, and tried the above recommendation. It still will not shut off. It cranks really quick and runs great. I’ve checked all the connections even on the new control box, switch and kill switch. Like he said before I replaced the manual oil pump, the reservoir tank on the side of the engine. I used all the original sensors. I had to remove the starter and the relay assemblies to have access to the oil lines on the manual pump. I then put everything back as it was. I had not ran it in a good while. I’m not sure why this started. I’m sure it has something to do with what I’ve done but I’m not sure what or how. I really appreciate any help that you can offer! Thanks so much.

[One Ocean]

My guess is while taking off the oil tank you have disconnected one of the grounds - a black wire that connect directly to the block. When putting everything back you may have forgotten to attach this ground, or tighten it.

There is one grounding wire where the engine will exhibit exactly what you explain, everything seems perfect, but you cannot shut it down with either key or kill-switch.

Have a look around the area that you worked on and I wouldn't be surprised if you indeed find a loose or poor grounding cable.

[Rennerjd]

Thanks for your advice! I will try to go over it again. It definitely has been frustrating to say the least.

[Rennerjd]

OneOcean, I have checked every single connection and replaced all ground wires on the motor. I even used my jumper cables as the main cables to rule them out. I replaced the starter too because mine had gotten weak. It still will not shut off. I have never seen anything like this before. I have a manual for my motor too. I have been going through it to see if I have missed one little thing. The only things I haven’t replaced are pulsar coils, stator, and rectifier. It runs great with no issues other than getting it to shut off. I have been going over this boat for about 6 weekends on and off trying to figure this out. I’ve called people and they are scratching their heads. If you have any more advice I sure would appreciate it. Thanks again!

[Rennerjd]

Hello if anyone can help me, I found out that what I called the cdi is actually the icu as noted in the picture below. The cdi is number 6 in the picture below. Could this be what’s causing my problem of starting but not turning off?

[Rennerjd]

I also remembered that when I started the motor after I had changed the oil pump it did start and turn off the first couple of times. I found this suggestion on the Internet also.
This has to do with an evinrude etec but it’s the same principle that I’m trying not to spend so much more money than I have to . I have spent way too much money now with the same problem.
Voltage regulators connect to the stator (2 yellow wires) and convert 10- 70+ volts a/c from the stator to 14.4- 14.6 volts DC (1 red wire). The tachometer is also connected to the voltage regulator and uses the incoming a/c frequency to drive the tachometer (grey wire)and they CAN and DEFINITELY DO CAUSE IGNITION SYSTEM FAILURES.
Stators have several circuits which include battery charging system, ignition high voltage supply, ignition triggering and timing, as well on the Etecs it provides 70+ volts AC to fire the hpdi fuel injectors. Any of the systems connected to the stator can cause ignition issues. These include voltage regulator, power pack, timer base, ignition switch, kill switch, over heat sensor, shift interrupt switch, tachometer, Etc.
Thanks for any help.

[Rennerjd]

I have done some more tests and it appears that my rectifier is bad on the Green #2 lead. It failed the continuity test for that leg. This wire comes off of the rectifier and goes up to the lighting coil, charging coil, pulser coil. Could this be my problem?

[Rennerjd]

I have finally found what it was and fixed it. The regulator and the power pack had a bad leg on it. One thing is for sure it should last another 30+ years now a lot of new parts.

[Vrybusy]

Glad you got it figured out....now its time to go fishing!