first you need to know how to actually use the calculator. the props I gave you will get you close. it takes a lot of data logging and experience to actually punch in the right parameters.
second, 12s is only good for about 7kw. Lipo's only out put 140-150A on cheaper side, and 175-185A on the higher end side of batteries. Multiply voltage under load by the realistic amps to be pushed. 41v X 150A = 6150w. For 7 minute runs you want to stay well below the motors max ratings. with a boat that size aim for 16,000-20,000 RPM to put you in a prop range of at least 62mm and up.
here's a sample of the calculator with parameters I find pretty consistent with reality both engine RPM, battery voltage under load, and prop slip....20-25%.
Screenshot 2023-11-24 6.09.59 PM.jpg
you are generally going to have to buy 2-4 props before you dial in the system for runtime and speed. Since you want a wildly long runtime you should go as high of voltage and low of KV as possible and get the amps down to under 100A. 18s to 20s would be pretty good to get you there.
an example: my 42" catamaran with 12s running 60mph could do 5 laps of 16 seconds around the race course and the batteries would be 20% left. 6500mah packs weighing 540g each. About 90 seconds runtime maximum @ 7,000w. There's an other member here that runs 86mph in his 42 cat with twin 56mm motors and pulls 13kw to go that speed. 6500w per motor. So, 7 minutes is over the top long and basically unrealistic unless you run at 40mph or something. 60mph and 7 minutes in a boat that large is a gargantuan task. the boat will need 2 people to launch and weigh over 25lbs.
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