Lost tach function

[Cruiser_85]

Replaced two original MerCruiser 350's (sn. L662182 on one, 1,300hrs+ on each) with 350 MPI Bravo Quicksilver (8M0136294) engines. Connected the 10-pin connector and cranked. Engines run, all gages except tachs function, though oil pressure appears low for new engines, >20psi @ startup, drops to near zero when warm (full of 25W/40), will check with mechanical gage. Found a grey/white cable labeled TACH in the Lube Bottle sending unit harness. There is a grey wire in the harness from helm to engine bay at the 10-pin male connectors, haven't unshrouded the new harness to attempt to trace the corresponding cable at the female connector. Thought I would ask first, where should the cable labeled TACH in the new harness terminate? Thanks in advance.