How to jump a mercruiser connector?
 

I need to program an ecu on an engine that is not in the boat. Can someone tell me how to jump the round merc plug in so I can simulate key on engine off?

follow this diagram

you probably need to energize the purple wire (ignition) in the harness...thats usually the standard color for ign....since there are different plug arrangements you would need to test the harness to find the right pin. I know there are 9pin and 10pin round harnesses...not sure if any others
Im sure you will need to hook up a ground to the engine and 12v+ to the starter just like it would be in the boat other then that you would need a wiring diagram to see if there's any other secondary wires that need to be energized to the ECM

Ayuh,... Just hook the power to the coil's (+) terminal,...
That'll power the Ignition circuit,....

No typical coil on this one, HEI type

Why not install the computer in a boat with same MEFI and program it that way? I assume you have the bin file and just want to download into the controller.

Not knowing the year or serial number of the motor I'll provide both 10 and 14 pin connector info:
Connect battery to starter and engine block

For 10 pin connect, jumper pins 5 (Purple) and 6 (Red/Purple)

[ATTACH=CONFIG]565509[/ATTACH]

For 14 pin connector. jumper pins A (Pink) and C (Purple)

[ATTACH=CONFIG]565510[/ATTACH]