Maintenance on my 1GM10 Yanmar

[JerryW]

I'm coming up on my first maintenance (50 hours) on my Yanmar 1GM10 and I'm required to drain the water separator. I've found an excellent website which describes this (as well as bleeding the system).

Question: After draining this water separator, will I need to bleed the engine?

I find very little information on my water separator (a Yanmar 4230B). There is a pump atop this device. Question: what exactly does this pump do?

Lastly, on one of the numerous forums, I found this: "it is important to close the water intake when you are cranking the engine to bleed it, because it can pump water into the engine and then you got big problems. so right after you start it, open the water thru-hull."

Question: How would coolant water make it into the engine in this scenario?

My manual is an "operational manual" and is lacking in detail.
Jerry

[perchance]

Raw water enters the engine during cranking because the pump is moving water through the system but without the engine running there is no exhaust gas to blow the water out of the exhaust and it backs up into an open exhaust valve.