I start my turn with a scuttle readied in base I move it to star spring and conquer then I play first mate and ready the scuttle then use star springs effect to bounce scuttle to base readied to score the other battlefield, is this legal or does the star spring move exhaust my scuttle?

Yes, that line is legal — Star Spring's move does not exhaust your Scuttle Crab.

Only the Standard Move's cost is exhausting the unit (Rule 144.2 / 420.3.a). Star Spring's ability is an effect-driven Move (Rule 449), and since it doesn't say the unit is exhausted, the Scuttle simply arrives at base in whatever state it was in. Since First Mate's "When you play me, ready another unit" already readied it, it lands at base readied and can Standard Move again to the other battlefield (no once-per-turn limit on Standard Moves, as long as the unit is readied).

Two housekeeping notes: when you play First Mate at Star Spring, both First Mate's trigger and Star Spring's trigger fire at once and you choose the order — either order gets you there, since First Mate can ready a unit at base too. And the two scores are on different battlefields, so the once-per-battlefield-per-turn limit (Rule 470) isn't an issue.