TY... just never encountered red gear oil in a marine application.

I have no personal experience with the Redline Syn gear oil, but - the Amsoil synthetic gear oil in a B-drive will act up with delayed shifts and the noises that follow due too much slip in the cone clutches - not sure if that is relatable to your oil or not - just putting that out there for consideration.

Amsoil is was what the shop had in stock and was available. What is your recommendation? It is only been in there for a day and not even been run above idle.
Is this the recommended stuff:

Mercruiser HP gear lube as you have pictured is the normal lube used in Bravo 1's.
Quicksilver HP gear Lube is the EXACT same gear lube and is just packaged/labeled for regular retail stores. $10 at Walmart.

Are you sure the clanking is not your internal exhaust flappers??

Great question. I hear (and feel it) in this area:

Your top gear set/ cone clutches is right under the cap..... If the issue was mine, I would drain and refill with the Merc High perf. gear oil and see if the problem persists.

Even at the cost of the oil, it is cheaper than having a tech diagnose the issue where the synthetic gear is a possible cause... even 1 drive just to eliminate the possibility.

If it persists, you are into parts.

THANKS! I WILL change the oil. I had no bits of gears in my drained fluids and nothing on my magnetic drain/vent plugs. There is another thread about the shifting fork rattling/bumping and I am kinda hoping its simple like that.
abnormal noise coming from bravo one

Idling in neutral, mine will make a sorta rhythmic knunking sound at times. Other times I don't hear it. Mine sounds like it's behind the eng. I was told it's the input shaft rattling inside the drive coupler when it's spinning with no load and it's nothing to worry abt. Never tried listening for it outside the boat but I could see the knunking transferring into the drive. Try listening behind the eng for the sound.

Go with the Merc/Quicksilver lube for sure. It's good stuff.

Probably just gears clattering with cam overlap.

I would like that...I will be reunited with the boat in 10 days for more analysis/investigation.

Are you saying engine cam overlap? That is curious because I have just reduced the engine idle rpms to reduce stern drive engagement stress. The warm engines would hover about 1,000-1,100 rpms and I reduced that to ~750 rpms. I wonder if this is a new/induced vibration/noise due to that.
I have been warned about reveberation, so I may bump them back closer to 850...and maybe solve the issue.
KEEP THE INPUTS COMING... I take them all in and am getting a lot of good advise/experience.