2006 Mercruiser 8.1 Starts Then Immediately Dies

T

TheBobC

Member
Sep 21, 2017
79
Pompano Beach, FL
Boat Info
1999 400 DA
Garmin 1242xsv, 742xs, Fantom 24 Radar
Highfield 10.2 Tender w/Tohatsu 9.9
Engines
Cat 3116
Engine ran great three weeks ago. Went to go out today and the starboard engine would turn over and start as normal but immediately shut off (one second or so). Thought maybe it was my (not so) friendly Gen 3 Cool Fuel unit, so I put a gauge on the rail valve. Got 43lbs when switch turned on. Stayed constant when starting and dying. Checked port engine and it was similar (41)

Any thoughts about where to check next?
 
Does even faster (will not start) if any throttle at all.
 
Sadly, went to the boat yesterday and swapped out the IAC. No difference. The engine starts and sounds normal for literally 1 second and then just dies. No error codes on Smartcraft.
 
monitor voltage at the 50 amp breaker next time you start it. crank and cam sensors won't throw a code. PCM needs at least 11 volts to fire the coils.
 
The 8.1 in my truck did that. Needed a crank sensor.
 
Been busy, just made it back to the boat today. Decided to swap all engine sensors one at a time as well as computer to see if I could determine the problem. Long story short, it was the MAP sensor. By far the easiest to get to, so of course it was not the first thing I tried. Sheesh, always start with the easy! Anyway…does anyone have any experience with using the $28 part for generic 8.1 l as opposed to the $250 part from any number of marine places?
 
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