More merchants sunk, I guess. Then the US simply closes in on Japan faster and more bloodlessly, but I don't think that the surrender would happen any sooner than it did.
I'm afraid you're very wrong. Changing nothing but the torpedoes, the Pacific Fleet Sub Force could bring the Japanese economy to ruin by the end of '43. The impact on the island-hopping campaign is bound to be pretty substantial, too. (Loss of CVs means CPac ops likely are delayed a couple of months. If you are willing to butterfly away the stupid Makin Raid,

maybe not...

)
That said, I should point out, it was actually the loss of the "
maru code" that was the more important factor...
Yeah, the US would still need to pursue an island hopping campaign to secure airfields for strategic bombing of the Home Islands.
With the ability to close Japanese industry, & prevent shipping of weapons & supplies, I wonder why strategic bombing even becomes necessary?
Forcing those Japanese strongholds to wither on the vine might help a bit in taking the islands
Might?

Undoubtedly would.
but I don't think a submarine blockade would end the Japanese fighting resolve as effectively as strategic bombing.
Maybe not resolve. Certainly the ability to continue. Widespread starvation was certainly a prospect. How does this affect Japan's willingness to fight on?
Early on, expect a dozen or so extra merchant ships and transports sunk. Throw in another couple of destroyers and cruisers.
More like 30 or 40 merchants, & that's changing nothing else.
The big advantage will be when the US carriers attack with working torpedoes. An AU Coral Sea with the US having an extra carrier and working torpedoes for the torpedo planes will ruin Japanese southern movements.
Wrong. The Mark 13 was a completely different design. If the Mark 14 works, tho, it's likely the Mark 15 (DD equivalent) works better, too, so DD ops are also more effective. (How you measure this, IDK.) Very good chance of more IJN warships sunk; IMO, low chance of it being a
lot more, given the conditions DDs fight in.
With better torpedoes earlier in the war I would consider it possible that with the earlier losses of Japanese merchant ships it is entirely likely that they would change their strategy and thought regarding antisubmarine warfare since it would before apparent that something would have to be changed to increase their ability to fight the US.
The Imperial Japanese Navy starts an intense crash program updating its antisubmarine warfare tactics and US submarine losses rise by late 1943 that operations are suspended in the waters immediately around Japan.
Don't make me laugh. IJN attention to ASW of any description was (in the words of a senior admiral) "shiftless".

USN boats dramatically improved their score in '44 over '43. Did IJN respond? Not in any systematic way. There was scant convoying, DDs still got priority for the fleet, air patrol was nearly non-existent...
I think working Torps -Withor Without Carriers would shorten the war significantly............ Provided the US starts a program of targeting Tankers & Troopships from Early 1942.
Putting tankers at #1 priority from the start would be a great idea. Persuading Nimitz to start mining Japanese harbors (Truk, Saipan, Rabaul) instead of insisting on sub surveillance, freeing them for more productive use, would be a good idea, too. Not basing boats in Oz would be a terriffic idea, since it would free up the Luzon/Formosa Straits, which were probably the best patrol areas; OTL, they were off-limits due to fratricide between Oz & Pearl boats. It would also help to keep Lockwood from diverting boats to supplying guerrillas in the P.I. (which was never more than a trickle,

but a waste of patrols, & Lockwood was inexplicably enamored with it

).
If, indeed, Nimitz is forced to rethink strategy by lack of CVs, some of this might actually happen.

Japan is even more f*cked than OTL.


(Is that possible?

)
Can you say, "VJ-Day 1942"?

As with every other WW2 navy, US pre-war training for sub commanders was lacking, especially the emphasis on tactics which, while worked well in theory, proved nearly unworkable in practice. Quite a bit of "dead wood" needed to be weeded out of the CO and PCO ranks once the war began.
There was a learning curve for the flotilla commanders ashore too. The US sub force wasn't immediately or solely directed at Japan's merchant traffic or oil tankers the weakest link in that traffic. The emphasis on commerce destruction didn't take place until late '43 and subs were still regularly diverted by Ultra decrypts on low odds intercept attempts against IJN warships throughout the war.
Working torpedoes and more Gatos in 1941 won't disembowel Japan's merchant fleet in 1942 as long as the men and the thinking commanding the boats and choosing their patrol areas remain the same.
True on all counts. However, as I said, you can still wreck Japan's economy before mid-'43 even without a radical change to training & doctrine in the '30s, which changing this would require. You can get some of this by firing English & making Lockwood ComSubPac sooner (tho Lockwood was pretty damn junior...


).
he old torps still used by the WW1-vintage S-class boats were IIRC without any flaws.
Correct. Had USN standardized on the Mark 10 (& produced the hell out of them, which NTS wasn't doing; in 1942, the rate of production by NTS was still only 2.5/day



), the problems would've been solved. Except, the smaller warhead meant it would take more Mk10s to do as much damage...& you may end up with no more actual sinkings.

