Re: Safe to run drive fully trimmed up?
I moor my boat in skinny water (about 3 feet depth at low tide).
So, out of necessity, I run the outdrives at about 3/4 tilt and at idle RPM (600 or so) . . . but don't tell anybody.
I would not run the outdrives in the full up position, because the u-joints will get mad. And I would not go above idle speeds if the outdrive is up in the 'tilt' range.
If need be, and when you have the opportunity, take a look at what tilt angle on your trim gauge gets your outdrive reasonably close to the level of your keel . . . that way you have an idea of how far you really need to tilt the outdrives to improve the draft of your boat in skinny water situations.
Another thing you can do in skinny water is have folks go up to the bow while you go through it at idle speeds. That way you won't have to tilt as much.
My biggest concern when traversing shallow water is hitting a rock or a mooring anchor/chain or something. You would want the skeg to make contact rather than the props, particularly with a bravo 3. So, you should have an idea of how far you need to tilt the outdrive to get the props up out of harms way.