Your post made me sad in so many ways.

I have only one crew and its a KM with 5 engies and 3 reps.

None of my sailors are elite, but they all have 180 vets, does that mean I will never have a decent repair rate? 

Major potential that your repair rate sucks even with 180 vets . Unless you get some 11/12 or 12/11 engie and some other gimp set up.

12/10 engie and ellite repair do fine. It will have decent repair rate, but don't expect to be like UK.

So with 11 base engineers and 11 base repairs it is going to suck with 5 engies 3 rep all with 180 vets?

Well, like 99.99% of all players the first crew is not perfect, BUT:
- each base value missing will cost you only around 3-4% absolute ability
- no, you wil probably not reachrep cap with 3 reps base 11 and other sailors not at perfect rep side stat
-  we are talking about maybe 15 seconds repair time from almost dead to full repair. How many situations you had were this was really of importance?
- having 180 vets is already very good.

Conclusion: That crew will  hit all necessary caps (speed, accuracy, reload, SD) but lacks a bit in repair and overheat time. No reason to through it away and still offers a lot of fun.

Next crew you know what to look for: Best primary stats and good secondary stats (rep, restore). I would prefer a 12/10 or even 12/11 (e.g. engi/rep) sailor over an elite one any time.

side note:
It's so easy here to help "bad base" crew. On NFEU servers a boost (prem sailor) gives only 10% instead of your 20% additional ability but costing same money. You can even make base 10 or 11 sailors decent working on NFNA by using that.

Ok... well is hitting the cap worth it and is it true ill need  5X 12/10 engis plus 3 EBVE reps to do it?
If not what if  I boost the engies?

For KM the secret is putting yourself in situations where you dont take hits. Chances are you are going to be 2 shot if you do so whats the point of rep cap? :P