How should Dashi made with kelp and bonito flakes smell?
Since dashi is, after all, made with seaweed and dried fish, it will smell and taste a bit of the sea.  If you don't eat or prepare much seafood, this smell might seem quite strong to you; for people, like most Japanese people, who eat fresh seafood five times a week, the smell and taste are subtle.

The other possibility is that you made an error in preparation which caused the stock to become far too fishy.  Any of the following can cause this:


using very low quality kelp or "instant" bonito
using expired/rancid bonito
allowing the pot to come to a roiling boil with the kelp and bonito in it
forgetting to rinse the kelp first
adding too much bonito, especially instant bonito
letting the dashi steep much too long


I would suggest that you back off on the quantities of ingredients you are using, let them steep for a shorter time, and make sure the pot doesn't come to a boil.  Clearly, whether or not your dashi tastes like it should by Japanese tastes, it's fishy to you.

EDITED TO ADD: also, if you don't eat seafood regularly and are finding even good dashi much too fishy, consider making dashi with konbu and dried shitake mushrooms instead.  This is commonly done in Japanese Buddhist vegetarian cuisine and is quite good.

Also, you might go to a good Japanese restaurant and get some kind of clear soup so that you can taste what you're shooting for.