vibration from leg

[174ben]

Hi all, took my boat out on the weekend and developed a minor vibration coming from the drive unit.

Vibratrion is there when cruising slowly off plane and turning slightly left or right. Its also noticable when trimmed all the way down and slow speed.Once moving on a plane at speed there is no vibration at all.

Im hoping someone could tell me is it gimbal bearing? or perhaps U joint? and or how to diagnose...

upon inspection ive now noticed excessive movement, around 1.5 inches left and right of the alpha one leg. Now im very concerned....

Thanks