Is this a good prop bet ?

[lasmoody]

Last night I was at my local casino and this guy says that he will bet even money all night that each flop will contain either a jack, seven or duece.

My reasoning was that he had (12/52) so 1 out of every 4.3 cards would be his and since we are only taking 3 cards that I had the best of it.

We ran it for forty hands straight at $5 a flop and I quit after losing $75. Afterwards he told me that mathmatically he was 53% to win. I've been stuggling with this and need some clarity as to the exact odds.