The verb in Hebrew is וְהוֹשַׁעְתָּ֥ which is hifil, perfect, 2nd person, masculine, singular with the waw consecutive of ישׁע. The KJV took the waw as a waw consecutive essentially giving the verb the meaning of the imperfect. While the YLT took the waw as a waw copulative leaving the verb as perfect. YLT doesn't seem to match the context. What's interesting is most of the modern translations translate this verb as imperative. The accent on the last syllable of the verb in the MT indicates the waw consecutive. Thus, the KJV is a more literal translation of the MT.
Note:
Whenever the perfect form is preceded by a waw it may be a waw consecutive or waw copulative. (Cf. §21.1 and 21.4.)
Van der Merwe, C., Naudé, J., Kroeze, J., Van der Merwe, C., Naudé, J., & Kroeze, J. (1999). A Biblical Hebrew Reference Grammar (electronic ed., p. 69). Sheffield: Sheffield Academic Press.
-וְ + perfect form may constitute a waw consecutive + perfect construction (wc. + perf.) that has a function similar to that of the waw consecutive + imperfect. (Cf. §21.3.)
Van der Merwe, C., Naudé, J., Kroeze, J., Van der Merwe, C., Naudé, J., & Kroeze, J. (1999). A Biblical Hebrew Reference Grammar (electronic ed., p. 164). Sheffield: Sheffield Academic Press.
§21.3. Waw Consecutive + Perfect
A distinction must be drawn between waw consecutive + perfect as analogous to waw consecutive + imperfect and cases where waw consecutive + perfect is simply a perfect with a conjunction, a waw copulative (waw cop.) with a perfect. The latter cases occur seldom. The so-called waw copulative + perfect can be distinguished from the waw consecutive + perfect by the fact that the final syllable of the latter construction carries the accent.
Van der Merwe, C., Naudé, J., Kroeze, J., Van der Merwe, C., Naudé, J., & Kroeze, J. (1999). A Biblical Hebrew Reference Grammar (electronic ed., p. 168). Sheffield: Sheffield Academic Press.