I'm confused about battletech morale mechanics. I did all the Argo upgrades to get the Morale up to 50 but when the misson starts the blue bar is low, barely enough to to one precision shot. So I wait a while until it gets full.

Are you playing with the newest patch? The Morale system has been changed and is now a bit different; it is now called Resolve, and though it is influenced by your crew morale, it is not exactly the same as your morale used to be.

Your bar will start low - indeed, if you hadn't built all those things, it would start so low that you would probably not even be able to open with a Precision Shot. It will go up by a smaller amount than before when you get enemy kills, but a larger amount than before at turn end. The bar is also numbered differently, so it's an actual 1-100 instead of the old 1-50.

If you're not playing with the newest patch, I have no idea.

I think the intent is to push out the use of morale/resolve powers to the latter portions of the battle, where they coincide with the more decisive moments and create a greater sense of drama. If it helps, you can think of the resolve generation being boosted by morale as conditions aboard ship making mech pilots more resilient. and thus generate more resolve per turn as a result.

Fair enough. It's all good.

just makes bulwark even more OP than before, now you can't cover with morale powers if you don't take the skill....

In new patch (beta available now) all skills will be revised. But if you think bulwark is OP now, and you don't play online, just edit file: CombatGameConstants.json and change GlancingBlowDamageMultiplier and EntrenchedMultiplier to 0.75. It will change damage reduction and stability reduction from 50% to 25%.
I also recommend mods that try to bring CBT mechanics to Battletech (lower base accuracy, correct to hit modifiers, correct weapon damage and heat generation and many many more).

Just a heads up if not immediately obvious (wasn’t for me).
Morale boosting comm systems give the bonus to resolve every turn.
Big benefit from 0 weight item!