You are refusing to act though since you do not think that it is worth investigating although the stakes are enormous. That then is the irrationality.
Whatever you are doing or not doing you are certainly having a punt on him not existing if you think that God might exist.
This is basically the old false dichotomy of Pascal's Wager.
Firstly, by believing in one of the many god-concepts you are taking just as much of a 'punt' as an atheist who doesn't bother with any. The stakes are just as 'high' for the believer.
You may claim that you did some 'seeking' (although how you might rationally go about that is unclear) and found the 'right' answer but you would then need to address all the other sincere 'seekers' who came to different conclusions (the majority - no matter what your religion, most people think you are wrong). You would need to deny their sincerity or have to admit that seeking just isn't enough and that there is actually no clear path to the truth at all.
Lastly, although the idea of some sort of god(s) cannot be 100% ruled out, the idea of a just, fair minded, omnipotent, omniscient god with an important message for humankind can be ruled out because it is simply inconsistent with the observed world in which we live: there is no clear message from such a god.