Well I've got a few response of my own to your questions.
About range, ahead slow gives you by far the most range. It sucks putting around at 5 knots, but it sucks more not having enough fuel to intercept that fat merchant you've been tracking for an hour.
About detecting merchants - Don't rely solely on your watch crew. They can see up to around 7km or so on a perfectly clear day, and much much less when the weather is bad and at night. With the hydrophone, however, if you're manually listening with it you can hear targets up to 20km away. If you don't do it manually, and rely on your hydrophone operator, he will only start calling out contacts when they are around 10km away. Naturally, what you want to do is learn how to use the hydrophone yourself. It's not difficult, if you click on the FAQ thread on this site it will point you in the right direction.
Once you start using that thing at regular intervals, you won't have much trouble finding ships anymore. I go to about 20 m depth every hour and a half or so and have a listen. I average 1 contact every 8-10 hours if I'm near the east coast of England. If you're looking for high traffic areas, hang out near the ports of England or NE of the Channel (don't get too close, there are lots of destroyers.) Once you're in a high traffic area, just submerge every now and then and listen, or you may just want to stay submerged if you know you're in a good spot. No sense in burning fuel if you know you're in a good spot. Just remember, if the contact you hear has fast-moving screws, don't bother chasing it around. It's probably a destroyer. You'll get experience eventually and you'll love the hydrophone. You can get good enough with it that by the time you finally see the target you've been tracking for a while, you're submerged and right in his path, just waiting for him to cruise in front of you so you can nail him.
|