crank shaft size?

[welshswampy]

I've got a 6.2 in a boat and the crank pulley has a wobble as if the crank shaft itself was bent. I don't think this is the case as I would expect there to be oil all over the place (theres none at all) so I'm assuming there is a fault with the pulley
I've found a site that can supply any pulley but I don't know the shaft size, can anyone tell me what size the shaft and key are, or do I need to take the pulley off and measure it
Thanks
Nick