Honda 150 - wont stop cranking - key off

Boat started and ran fine, did oil change and gear oil change. Went to lake - got constant alarm - engine would not crank, brought home - hooked up battery charger - it signaled battery bad. Replaced battery - as soon attached positive lead - engine started cranking key off.

1. Removed Key switch - still cranks as soon as positive lead is connected.

2. removed wire from main assembly relay to starter - positive lead can be connected - but as soon as you connect wire from main assembly relay - engine cranks.


Starter ? Main Assembly relay or something else ? how do I check ?

possibly the Solenoid which gets activated by a relay is stuck on. Disconnect the small black wire to the starter that is a blade connection like a stereo speaker then connect the positive lead and see what happens. if nothing happens then when blade connection is unplugged then relay contacts might have arched together completing the start circuit. If it continues to start while the blade is unpluged the solenoid on the starter might be stuck.

had this problem a year ago. changed soleniod, started, ignition....finally decided to change out the entire negative battery cable. This is what finally fixed the problem.

I agree it's a "stuck" relay contact. And, I also think you have already diagnosed the problem.

I DON'T have the wire diagram for a 150 but looking at the 200hp diagram there is a white wire from the main relay to the start solenoid. The wire is fed by a relay located inside the main relay assembly. That relay is fed by a 30 amp fuse. If the white wire is hot at all times then the starter relay inside the main relay is definitely closed when it shouldn't be.

When you disconnected the ignition switch, you eliminated the possibility of that relay being commanded to close. So, unless there's a very unlikely short to power (which you can easily test for) on the black/white wire from the ignition switch to the main relay, then the starter relay points are stuck closed. So, you likely need a new main relay

Like I said, the wire diagram I'm using is for a 200hp but I'm GUESSING yours is probably similar.

Good luck.