Stepping off what is actually an Argyll Ferries foot passenger-only service at Gourock Ferry Terminal (the ferry actually runs into central Gourock rather than McInroy's Point, which is for the Western Ferries car ferry service from Hunter's Quay), we walk to Gourock railway station before boarding the 19:24 ScotRail train service to Glasgow Central, arriving there at 20:15 on Tuesday evening.We then board the 18:50 Caledonian Macbrayne service WF1 to Gourock McInroy's Point Ferry Terminal, arriving at 19:15 Tuesday evening.
So edited thanks...they conveniently run at the same time/durationStepping off what is actually an Argyll Ferries foot passenger-only service at Gourock Ferry Terminal (the ferry actually runs into central Gourock rather than McInroy's Point, which is for the Western Ferries car ferry service from Hunter's Quay), we walk to Gourock railway station before boarding the 19:24 ScotRail train service to Glasgow Central, arriving there at 20:15 on Tuesday evening.

Ah, no worries...perhaps they're trying to compete? If you're a foot passenger, you're not going to bother going out of town to the terminals, though...So edited thanks...they conveniently run at the same time/duration
From Argyle Street we board the 20:42 First Glasgow service 1 to Renton, opp Kane Street, arriving at 21:43 Tuesday evening.