My Fastech originally came with twin Gen VI 502's, which were rebuilt and upgraded to Merc 500 EFI's. The boat didn't come with oil temp or fuel press sensors or gauges, but am looking to add them.

The fuel system is CoolFuel2 per factory spec, I know most people run gauges from the factory - trying to figure out where the senders are located/plumbed? Plan to use the auto-meter full weep type gauges.

Oil temp is simple if the motors are out, is there an easy way to add a sensor from the top or side? My filter bases are not machined for sensors.

I don't think any engines came equipped with fuel pressure sensors stock. Most folks add them to the end of the fuel rail just under the plenum.

As for oil temp, you can use the 1/8 NPT port low down on the port side of the engine blocks, just above where the oil filter would go if it was in an automotive application. If your oil pressure sensor is there, you can relocate it to the 1/8 NPT port at the top of the bellhousing, just behind the intake manifold.

Our 500efi’s have fuel pressure sensors on the inlet of the fuel filter, but none on the fuel rail.

Oh, for the low pressure side of the system then? But nothing to monitor the high side?

correct

Yeah, the low pressure side doesn't tell much. I run the 2 pump system from Merc, not sure what a low side measurement would do to say a lean burn down at WOT. 525's have them on the fuel rails, sucks that the 500's didn't get them.

I'm ware of the Oil temp being on the bottom of the block - just impossible for my 220 lb body to do in a Fastech with motors installed. Was hoping they made 3 way fittings for either. May become a spring project.

Some ideas For fuel psi:
Remove to see if scchrader valve housing (#4) is 1/8npt. That is size if many psi senders. If it isn’t or if not enough room to put sender in there, see if there is if you drill and tap a hole in middle of #13 “45 degree fuel fitting.” Obviously remove if you do drill/tap, then clean and reinstall.

They should really add these sensor stock!

Didn't realize the Shrader was threaded - that may be a good option. I believe the 525 uses the other rail to mont the sender. All of the har piping is great, but amazed a 'race' engine doesn't come stock with an additional port ;(