Kyogre IV question

I'd power up. Unless you already have a better one, I'd give it some love. Power it up to 2.5k or so, or more, because Kyogre isn't coming back any time soon...

Attack is usually regarded as the most important stat, so if you need a strong water type for whatever reason then I’d invest at least a little into it. Weigh the cost of taking it to a breakpoint and see if it’ll be worth it. If you don’t need a water attacker then it’s up to you if you wanna spend dust or not

https://pokemongo.gamepress.gg/cpcalc#/
15a/15d/15s Kyogre at level 40 is 4074cp with 155hp.

Your 15a/15d/8s Kyogre will be 4001cp with 150hp. Same atk and def IVs, so same breakpoints. Just 5hp less.

How is your rare candy count? I don't think you would ever regret it, but if you need a water attacker, Gyarados may be a cheaper option, tho Kyrogre will always outclass Gyarados.

Do you need a water attacker right now? It's a pretty good Kyogre to get from a trade, but there's no reason to invest if you don't have a use for it.
Just keep it for now and wait until you either get a better one or you feel like you need to power up this one.

Kyogre is the only legendary that I have 3 above level 30, my lowest is 84% 15 att. Never regretted it.