350 mag soft alarm and intermittent stall

rstrale

Recruit
Joined
Sep 3, 2019
Messages
2
Any and all help on this as I am far from a marine mechanic and the ones that I am paying are scratching their heads.
04 merc 350 mag sounds 2 beeps every minute after 20 or so minutes under way. Boats runs fine... Another 15-20 minutes under way and it stalls at various speeds and loads and at idle.Starts right back up and then stalls randomly
New plugs,cap,water pump FI relays..... Computer doesn't show code even when in alarm state. ????
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
43,326
Computer doesn't show code even when in alarm state. ????

First I would say the "Mechanic" does have the correct tool to scan your motor. What are they using to scan the motor with?

What is the motor serial number?
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,348
Hi

most common reason for the old 2 beep and bad running is the IAC valve. Happened to mine.
Did not show any fault initially when it happened to me. Only the 2 beeps. Was also no sign of it hinting at idle as many report as an indicator. It just failed.
Other reason might be the SW pressure sensor or TPS.
amongst those 3 is likely your issue. The mechanic should have maybe picked this up though.
 
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