It's an electrical pressure sensor. The early 496s actually used the same part number for the water pressure and oil pressure sensors so keeping a spare on board served for both.

Yea, its electrical... It lives behind the motor above the bell housing mounted in the power steering cooler... This thing definitely has a lot of sensors and wiring but I doubt its more than any other modern fuel injected engine... Especially the later serial numbers with digital throttle and shift and axius steering.

On my 02 496, the water pressure sensor was at the sea water pump.

I mounted the Hardin pump to the stock bracket. I didn't have any issues with the way it was mounted.

Based on your name, sounds like the Hardin didn't fix your issue... :D