Not dangerous, I have a friend that had a 32' Pachanga with twin Alpha's that both spun RH rotation. No ill effects. But if you have Bravo's just do it right.

No such thing as a left hand or right hand Bravo 1. Their all the same. Rotation is determined by the cable connection on the shifter at the helm. Can certainly be changed easily. Beings it's a Bravo set up I think I would change it. Must not be much of a problem though if it's been run like this so far. I also have a friend with twin RH Alpha's on a 30 footer and has no complaints.

Your mechanic is not very smart then.

Nearly all twin engine boats with Bravo drives run with standard rotation engines and change prop rotation by reversing the drive rotation. Bravo's can spin either way.

Spin them out.

THANKS ALL - MY MERC GUY IS MOSTLY SINGLE/FISHIG/ETC JUST VERY CONSERVATIVE - RAISED HIS EYBROWS AT PUTTING A BIG BLOCK IN MY OLD 24/7 ...TOO MUCH POWER
BUT HE IS A GREAT WRENCH
ANYONE HAVE A HYDRMTV QIV 23 LH

What are the advantages or disadvantages to spinning them out rather than in?

Out=Stern lift. In=Bow lift.

Normally in is faster on most V bottoms. Downside is reverse around the dock can be tricky.

the boat will also lean over a lot more in turns, can be dangerous if you don't know what you are doing. Mine spin in, I get slightly better mpg, same top end though. Docking is a little tougher but I have gotten used to it. I did it for the bow lift.

jet what year is your boat?

Ext
1980 scarab-s 30'