Water tube came out of engine

[Carl]

I had pulled my lower unit yesterday and realized the water tube came out of the upper part of the engine. I was able to feed it back up and get it back in right spot and it will stay there on its own, but it falls out too easily. Has anyone else had this issue? How is the water tube attached on the upper end? Does the power head have to be removed to reattach? It is a 1988 Mercury Black Max 150HP.

Thanks

Carl