@ Jbx5, It's about 50Nm from memory, I did it a few times at 6-7 knots on my old RLM31 with no problems, now I can do it at 16-18 knots I can leave GY on a falling tide so get a push most of the way up and get to the bar 2 hours before HW just as the tide starts to run east and get in early with plenty of tidal window still open in case of issues.
Leaving wells to come back head out 2 hours before HW and take full advantage of that tidal stream, I've come past scroby against the tide at 6 knots and it took forever.
@ Cal, I have been in there in conditions like that but also watched it going, been bounced there, touched bottom there, nearly bowled over there..... With the old channel on an early entrance I always like the bit where you had to head straight for the beach and into boiling water and turn to port at last minute, seemed crazy but if you hit the beach the tide would take you straight off, the problem was bob halls sand the other side that the tide will take you on to and leave you well and truly stuck.
Once went out of there on a mates fjord27 with TAMD41a when all you could see from the quay was a wall of white water, all the way out I kept saying to him "If you are going to turn back do it soon or we HAVE to go at least 1/2 mile out before even thinking about turning", he went for it and it powered through admirably although his Mrs. was screaming and my Mrs. sat on the floor holding his dog down.