The 45's are not there for most of the ships. You can think of it as "simulating historical"
... The ONI manuals would include the information the USN had, which might be line drawings, might be photos, might be another skipper's sketch, might only be text...
We'll have to wait for CapnScurvy or one of the other knowledgeable fellows to come along for the full story on the Sugar Boats' sonars. I do know though that that weird-looking thing that looks like a lightning arrester on the fore deck is the head, and that has to be under water for you to be able to hear...