So this was used against me and I'm wondering if its actually legal

Oicunn gets close then dose a boost to use his ability

"After executing a maneuver, each enemy ship you are touching suffers 1 damage."

Ships with the Boost icon in their action bar may perform a boost action. To boost, follow these steps:

1. Choose the |1 Forward|, |1 Bank Left|, or |1 Bank Right| maneuver template.
2. Set the maneuver template between the ship's front guides.
3. Move the ship to the opposite end of the template and slide the rear guides of the ship into the template.

• A ship cannot boost if it would overlap another ship or an obstacle token, or if the maneuver template would overlap an obstacle token.
• A ship cannot boost if this would cause the ship to flee the battlefield.
• When a player declares a boost action for his ship, he must also declare which direction he is boosting before determining if he can complete the boost into that direction.
• If a player declares a boost action for his ship and cannot complete the action using the desired direction, he may choose a different direction or a different action entirely.
• Performing a boost does not count as executing a maneuver.

I let it go but no I have reread everything I would say its a no go or am I wrong?

Boost is not a maneuver and you may not boost if doing so results in an overlap, so oicunn's ability does not work.

Also, compare boost with daredevil, which IS a maneuver and would therefore trigger the ram damage.

but Daredevel is only a hard 1 left or right, you cant use it for soft 1/straight 1

"ACTION: Execute a white (Left Turn 1) or (Right Turn 1) maneuver. Then, receive 1 stress token."

FAQ
A ship that performs the Daredevil action follows all normal rules for executing a maneuver, except that the manuever is always treated as a white maneuver. Daredevil may be performed even if the ship would overlap another ship or obstacle; resolve the overlapping as normal.

Yeah shouldn't of been able to do it, can't boost into overlap as you highlighted yourself in the rules

Can't boost into an overlap. You can Daredevil into an overlap though.

Also I want to say the new rules reference of checking stress after manuver doesn't key you oicunn daredevil anymore?

but Daredevel is only a hard 1 left or right, you cant use it for soft 1/straight 1

"ACTION: Execute a white (Left Turn 1) or (Right Turn 1) maneuver. Then, receive 1 stress token."

FAQ

A ship that performs the Daredevil action follows all normal rules for executing a maneuver, except that the manuever is always treated as a white maneuver. Daredevil may be performed even if the ship would overlap another ship or obstacle; resolve the overlapping as normal.

That was the point of his post. Daredevil says to execute a maneuver, Boost you're just using a template. That's the difference. Which template the two allow you to use is irrelevant, he's just pointing out the difference and why Daredevil would have worked for your opponent when Boost doesn't.

Oicunn daredevil rebel captive gunner engine upgrade dauntless was the most fun I had when I first got my decimator. With dauntless and daredevil you can "bump" twice and then still shoot at them after they move with a gunner. Rebel captive was just for "defense" but also would slow down other turrets so I can just follow them around bumping.

Also I want to say the new rules reference of checking stress after manuver doesn't key you oicunn daredevil anymore?

Not at all; Oicunn, Dauntless & Daredevil still work. The only thing that's changed is that you can't immediately remove the stress any more, so if you do pull off the combo you won't be doing it again for at least 3 turns.