Banging head on transom!!!!

[Faztbullet]

Boat: 2008 80ft Summerset house boat with twin Mercruiser 5.0 MPI's and bravo drives.

Problem: Port engine runs fine below 3500rpm when run above 3500rpm tach pegs out and engine missing and then will quit, no alarms.

Tests and checks: Disconnected tachs at bridge and flying bridge,checked cap and rotor, fuel pressure ok, oil pressure switch ok, knock sensor ok, no codes or glitches with Diacom hooked up,all temps correct only thing havent done i

 

[Faztbullet]

Dont know what happened but only thing no swaped is PMC....

 

[Fun Times]

May as well try the ECM swap.

My first guess would be you may be having a problem with the crankshaft position sensor since the tach is acting up. It's a sensitive sensor and will cause unusual problems. Banging sound at the transom? Almost like a backfire type sound? If so, either cap and rotor, spark plugs, or plug wires or CPS. Is the cap original? The flat caps are known to kill the engine due to crossfire within the cap. Let us know, Good luck.

 

[Faztbullet]

The bangin sound is my hardhead beating against transom. The CPS checks ok but that dont mean anything, will swap CPS with new one if doesnt fix will swap PCM's

 

[MikDee]

Just disconnect the tach wire from the Dizzy Neg -, not the bridge,,, Why there? Go right to the source.

 

[Fun Times]

Hi MikDee, This coil is a little bit different then the old design coil. The coil has a coil driver and the wires plug into the coil driver vs the old type coil where the wire is held on by a nut. It would be difficult and not recommended to disconnect one wire from the coil on this model.

See item number 18 for an idea of what the coil would look like, http://www.mercruiserparts.com/Show...=50&bdesc=Distributor+and+Ignition+Components

 

[MikDee]

I see, sorry about that :facepalm: