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Engine continues to crank with key turned off!!!

Marauder 72

New member
Hey guys I have a 1989 3.7 Mercruiser The last time i had it out I tried to turn off the engine and it would almost die and crank its self back up the starter was continuing to run. After that I didn't have that problem again all day. Now im trying to get the boat started after it set for a year with a broken shift cable. Im still having issues with the cranking system. As i try to crank the engine it continues to try to start (sluggishly). I had jumpers cables hooked to the battery(s) cause they where dead. It would continue to crank till the jumpers where removed. The tips of the jumper cables would start to glow red hot as it was continuing to turn over. Once you disconnect the jumper cables you can then hook them back up and its fine till you turn the key to start it then it will continue to turn over. This engine has a relay/solenoid that is mounted to the engine block not on the starter. I replaced it this weekend thinking that since it did it with good batteries last time i was out that low current wasn't the problem and the same with the ignition switch it tried to turn off the engine last time i was out in the boat but the cranking system was still getting power from some where. So i thought if the solenoid WAS working then when i turned the key off the solenoid would stop the flow of power to the starter but it wasn't the solenoid. Im trying to figure all of this out but im stuck any advice on this problem would be greatly appreciated.
 
power to the starter can only come from the solenoid contacts. weak batteries can sometimes weld the contacts. other than that
power to operate the solenoid comes from the start position of the key switch
 
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