I have to purchase the second hydrophone multiple times.

[CjStaal]

I don't think my purchase is sticking. Once I buy the second hydrophone my renown goes down 300, I think it attaches, but the price doesn't go down to zero, it stays at 300. Is it still using the new hydrophone? Do I need to repurchase after every mission? How can I find out if it is being used?

[UKönig]

If I am not sure if my sub has a particular bit of equipment on board, I will attempt to purchase it. If I don't need it, I will get a message saying "you already have it!". If you do need it, you will get a message asking if you are sure. Click "yes" and a few days should get added to the in base calendar for the time required for the dockhands to install the new stuff. I don't think I have ever had to buy a piece of equipment a second or third time.

[CjStaal]

If I am not sure if my sub has a particular bit of equipment on board, I will attempt to purchase it. If I don't need it, I will get a message saying "you already have it!". If you do need it, you will get a message asking if you are sure. Click "yes" and a few days should get added to the in base calendar for the time required for the dockhands to install the new stuff. I don't think I have ever had to buy a piece of equipment a second or third time.

Ok thanks. I didn't know that it takes time to install. Also, I'm guessing the price never goes away then? It just stops you from purchasing it again if it is already purchased?

[Rambler241]

UKönig wrote:
I don't think I have ever had to buy a piece of equipment a second or third time.

I have - on several occasions. The first was right at the beginning of a 1939 career out of Wilhelmshaven with a Type II. In my ignorance, I assumed every Uboat would have a flak gun fitted as standard. When I realised my mistake, I restarted from scratch, and selected the 20mm available. It appeared on the boat profile, but while off the UK east coast a Hurricane appeared, there was no flak station - gone, missing, lost at sea. Restarted again, and this time it stuck.

The last was on a 1943 patrol out of Brest - I'd had the MAN engine upgrade for the previous patrol, but towards the end of this patrol, noticed the speed (standard) had dropped by 2 knots, and remained that way 'til the end. When back in port, had to select (and pay for) the upgrade again. I copied the career profile so I could check back through saves to check speed, and therefore the upgrade. It was there leaving port, but disappeared on the way to the patrol grid.

A hint for those who decide to restart a patrol from the "In base before mission" autosave - check everything you think you did when in base previously. The torpedo loadout reverts to default (for the date of course), and you may well find one or more upgrades haven't "stuck". I'm not sure whether you lose renown as a result, through paying twice for upgrades.

[UKönig]

I have had it happen that I lost my torpedo loadout. I bought a bunch of seekers (cost me a pretty pfennig too), only to find normal torpedoes on board, after mission launch.
I have an explanation for this. I think it's because when the seekers first make an appearance, they are considered experimental prototypes. Then they are withdrawn temporarily while improvements are made. Then they are mass produced and readily available after late 1943-early 1944, in greater numbers. That's why before 1944 I don't buy any seeker torpedoes and just take whatever special ones they (the game) sees fit to give me. No doubt this bug is one that was stomped out in one of the unofficial patches, but still gives stock players (they exist!) a headache.

[Lokisaga]

Also, I'm guessing the price never goes away then? It just stops you from purchasing it again if it is already purchased?
Hello,
Correct. Additionally, buying upgrades, changing the torpedo load out, or hiring and firing crew members should be the last things you do before going out on patrol. This procedure solves the problem of modifications and changes disappearing from one's boat.