47, no, it isn't unusual. Upper FSB limits for a G31/G41 motherboard is, on the average, around 350 MHz. But I have seen reported examples of as low as 342 MHz and as high as 363 MHz.
I have 3 Gigabyte G41's, one a DDR3 T model, in office PC's. One will run all day at 352 MHz, but fails instantly at 353 MHz. One will run past 360MHz FSB, but fails P95 after about 4 hours.
They are pretty good with a 200 MHz FSB CPU such as an E5200. Here, the overclock limiting factor is the CPU.
And they are not bad when used with a 266 MHz FSB chip such as the E6500 or E7200 series Wolfdales, even if you reach motherboard FSB limits before you reach CPU core limits.
But they are poor candidates when used with 333 MHz FSB chips. About the best you can expect is a 10% overclock before reaching motherboard FSB limits.
What do you expect from a $50 motherboard?