Starts but dies after i release the key

So I have a merk 1970 115 6cly. The problem I am having is that it starts fine but a soon as I release the key from start to run it immediately cuts out. The problem started I’m almost for sure because I switched batteries while the motor was running. I have since learned that is not the thing to do. Everything was fine until I took the one battery off connected the positive to the other battery first, then I connected the negative and that is when something immediately blew and the motor quiet. I took the throttle box apart and the key switch and wires look good but I’m not really sure if the actual switch is bad or not. I looked over most other wires in the motor and everything appears ok. I also read that connecting a battery while the motor is running can blow the rectifier. Would a bad rectifier cause my problem or would it just prevent for charging? Does anyone know what I may have damaged. Coil, switch, ect?

Usually a bad trigger or low battery voltage will cause this problem.

Chances are you switched batteries while the engine was running to charge a weak or dead battery. If this is correct, any voltage below 12 volts on this system will damage the ignition system. You cannot use a maintenance free battery with this system.

Check your fuses.

Chris thanks, Yes I switched to charge a dead battery. Hey ,what the trigger your referring to? I was in a bad situation on the water with my dead battery and kind of panicking cause I really needed the boat to run at that moment. I am going to get an ohm reader today and start testing things. Is there a way to test the key switch? Any suggestions on other things to test or replace? Thanks a bunch.

Get a DVM for testing. Check the voltages on the switch first and if needed label and disconnect all of the wires in order to stop feedback thru the wiring when ohm testing the switch.

Thanks guyjg I am going to buy a multimeter today. Sounds like i need to just start testing things. I will start with the switch. I'm a carpenter not an electrification so wish me luck. The mercury manual does a good job at explaining most of the tests for the ignition parts. I'll update with my results.

Ok so I went out and bought a multimeter and tested a few things. The book i'm using says to set my omhs to r1 or r100. my multimeter does not have that setting so im using the settings on the multimeter which are 200 and 2000. I can't really test correctly though because the specs in the book dont match the setting on my multimeter. The only test that failed was the diodes test in the rectifier. I have not tested the switch yet but I'm thinking it's ok because when i switch the key to run the gauges go on as usual, but im not ruling it out as the problems. Would bad diodes make the motor cut out like this when I release the key from start to run? I'm still kind of stumped here and i'm not sure if i'm more or less confused when I started this morning. Any other advise would be much appreciated..Thanks Jonas

...I can't really test correctly though because the specs in the book dont match the setting on my multimeter.

Click to expand...

Use the 200 scale and dived the result by 2 when comparing to the book chart.