This is one reason you lower the out drive...

[nola mike]

When I have a shallow mooring spot and have to keep the drive up, my habit has been to tap the trim down about 6 secs to lower it about 1/2 down.
Here's a tip for old tech guys with old tech boats:
Time how long it takes your drive to go from full up to full down. Mine takes 12 Mississippis lol. So I count down 6 Mississippis and I'm half way down and that's fine for the U joints and won't hit bottom at that point the boat only draws about 2" of water.

I've heard that people also have " trim gauges" that work. I think I had one of those once

 

[Lou C]

Mine actually works, I found that the Sierra trim sending units for the Cobra last longer than the OEM ones, that lasted about 2 seasons in salt water. However, the trim gauge is of limited value in terms of knowing how far down or up the outdrive is. I found counting down from full up or full down and setting it half way, is the way to go.
PS that 2" of water should have been 2' lol.