SE Version 0.1.6.121 includes a few K2 Compatibility changes, one of which is reducing the energy capacity of water/steam from 0.5Kj to 0.3Kj. As a result, the Fusion Reaction outputs 40% less energy, and the K2 Advanced Turbines are limited to 120MW output when using 1935 degree steam.

Hey a WorkAround is to change the Data-Final

1935°C Steam

krastorio.recipes.replaceIngredient("kr-fusion", "water", {type = "fluid", name = "water", amount = 173600})
krastorio.recipes.replaceProduct("kr-fusion", "steam", {type = "fluid", name = "steam", amount = 170100, temperature = 1935})

5000°C Steam

ingredients = {
    {"dt-fuel", 1},
    {type = "fluid", name = "water", amount = 66900}
},
results = {
    {"empty-dt-fuel", 1},
    {type = "fluid", name = "steam", amount = 65600 temperature = 5000}
}

900°C Steam

ingredients = {
    {"dt-fuel", 1},
    {type = "fluid", name = "water", amount = 376600}
},
results = {
    {"empty-dt-fuel", 1},
    {type = "fluid", name = "steam", amount = 369100, temperature = 900}
}

its 900°C steam because my Condenserturbines cant use 975°C

if you want 975°C change the values to 347200 water / 340300 steam at 975°C

you may notice you will get less steam from water because its the 98% effi

greetings MoSIi

PS: calculated with this formula https://wiki.factorio.com/Steam

The water/steam will be lost in the turbines anyways, no real reason to lose it in the heating process too.
High temp fusion was set to 90% efficiency by this mod author, so the steam yield should be around 60k.
100[GJ] x 90% / .3[kJ/deg] / (5000-15)[deg] = ~60k
I do agree though that the low temp recipe should be adjusted to 900 degrees because that is the effective temp of the condenser turbine.
100[GJ] x 98% / .3[kJ/deg] / (900-15)[deg] = ~369k