Mercruiser black scorpion 5.7 - holley efi
 

I would like to update my 1997 5.7 black scorpion to a simpler and more modern EFI systems. Here are my thoughts

- holley sniper and a new intake (o2 plate in exhaust)
- holley terminator on current intake with rebuilt injectors - ditch map for o2 plate in exhaust
- vortec intake with carb

the sniper EFI seems really easy to get rolling and with a benefit of closed loop fueling. Anyone done this on a not catalyctic engine? How long are your o2 sensors running? Can I run the sniper in open loop if it fails?

Generally I am just looking for some insight on direction, I can clearly tell the existing fuel rail and intake are nice, so potentially the terminator is better? If I go carb for simplicity, what is the best way to test AFR while setting it up? Thank you all!

I am fairly positve you can run the Holley in closed loop once tuned. O2 sensor life varies on location and how much water gets in or near the sensor. I run the Innovate O2 heat sink bung extender (HBX-1) on my application and have gotten about 10 years of conitnual use.

If you go for carb you can monitor AFRs with wideband and a dash mounted gage or handheld unit. Dramatically helps with troubleshooting when on the water.

I wouldn't use the Terminator ECU in a marine application.