Starter solenoid staying energized with key off

[Duro78]

2000 merc 200 2.5 efi. With perko switch off i changed starter solenoid and relays. Turned perko switch on and all was well proceeded to pump ball also changed filters and rebuilt lift pump. On several occasions key worked fine while trying to start til i turned it off and the starter kept cranking. Quickly turned key on and off again didnt stop so i ran back to the perko switch to kill power. All i can think of are the solenoid contacts closing shut and not opening when the key is turned off. Yes a brand new solenoid can fail but thats just not vibing with me if it did would like to know why. Also while googling the issue i read of a guy having the same problem changing solenoid and problem persisted, wasnt til he changed out his starter it stopped. The thread ended without an explanation. Now i cant turn the perko on without the starter immediately starting to crank.Going to change the solenoid in the morning ran out of daylight but i dont want to run into the same problem. Thanks you

[JR IN JAX]

Unless the coil is getting constant power, the contacts are welding shut. Almost all high current contacts are made from cadmium with a silver coating. The flash of the silver surfaces when closing melts a small amount of the silver surface and allows it to carry a lot of current through the melted silver. The spring pressure breaks the bridged silver when deenergized. Once the silver is depleted or splattered, the contacts can weld together. Normal operation leaves a black coating of oxidized silver.

Clear as mud?

[lpugh]

2000 merc 200 2.5 efi. With perko switch off i changed starter solenoid and relays. Turned perko switch on and all was well proceeded to pump ball also changed filters and rebuilt lift pump. On several occasions key worked fine while trying to start til i turned it off and the starter kept cranking. Quickly turned key on and off again didnt stop so i ran back to the perko switch to kill power. All i can think of are the solenoid contacts closing shut and not opening when the key is turned off. Yes a brand new solenoid can fail but thats just not vibing with me if it did would like to know why. Also while googling the issue i read of a guy having the same problem changing solenoid and problem persisted, wasnt til he changed out his starter it stopped. The thread ended without an explanation. Now i cant turn the perko on without the starter immediately starting to crank.Going to change the solenoid in the morning ran out of daylight but i dont want to run into the same problem. Thanks you

This is usually caused by high current flow as mentioned above, Low battery state of charge, inadequate battery capacity, resistance in cables, excessive starter draw or excessive mechanical rotating resistance, Low voltage to the starter will cause a increase in current flow, all these things can damage the contacts in the solenoid

[Duro78]

This is usually caused by high current flow as mentioned above, Low battery state of charge, inadequate battery capacity, resistance in cables, excessive starter draw or excessive mechanical rotating resistance, Low voltage to the starter will cause a increase in current flow, all these things can damage the contacts in the solenoid

The battery was brand new but sat over the winter. I checked the voltage before doing all this but i guess it wasnt adequate. So if i charge battery and change out the solenoid all should be well? Fully understand the other variables you mentioned could also lead to the same happening again

[Duro78]

Great info was wondering where the blk coating on my other motors came from. Going to charge the battery and change the solenoid and try again in the morning. Thank you for the info