Need a 12v+ when engine is running

[Punch'Eau]

Source of the post You should already have one for each engine. Take a look behind the helm. Mounted somewhere or tied to the harness should be an alarm horn/beeper/buzzer. If your key is on and the engine isn't running (no oil pressure), the alarm should be sounding. Same happens when you go to start the engine; turn the key to on and wait (delay circuit), the alarm should sound. If it isn't there's an issue somewhere; wiring, beeper/buzzer, pressure switch, etc. Same beeper used for an overheat.

By any chance, do you know where the purple short wire of the buzzer goes??? It has a fork type terminal and it was disconnected for both engines.

[Punch'Eau]

Source of the post Ya I agree, you need to determine why she is stalling to begin with. The IAC is a good place to start, could also be an ignition issue. When did she last have an ignition tune up?

I don't know when was the last check up. I bought the boat in June this year and the problem was there. I tried to swap the whole throttle body with port engine and it was nt better so the IAC is good?
I ordered new spark plugs just to be sure even if the previous owner told me they had been changed last year...
Thanks a lot