Going from memory – as I’m not on the boat just now – the left-hand one (with greater range, up to 150 psi, is the ENGINE OIL pressure gauge, and the right-hand one should be the GEARBOX OIL pressure gauge.
I’ve marked mine with a little white chinagraph-pencil mark on the black surround at the optimum pressure readings, so that I can see at a glance if all’s well (..or if oil’s well). Ditto with the temperature gauge ..so that I can see if the engine’s getting anywhere near its 99-degree TOO HOT mark.
(..And I ALWAYS check the oil level of both the engine AND the gearbox before setting off anywhere ..in Dover, the other year, I found that the gearbox was full of margarine: cracked gearbox oil cooler, so I had it replaced by those very nice engineering men just outside the marina gates, having replaced our ENGINE OIL cooler a year or two before. Now they should both last another 30 years.)
(..Wow, this great on white is almost impossible to read while I’m typing!..)