Big Block Actual Dimensions
 

Hi, I have a total 'newb' question regarding engine sizes; are the various sizes (454, 502, 496, etc.) just based on bore/stroke using the same block or are they actually different size engines completely? If, for instance, my boat had twin 454 mags, would I be able replace them with Mercury Racing 540s or maybe Procharged 502s?
I'm toying with the idea of a Scarab Panther and they usually seem to have 454s. If I wanted more power could I have them converted to 496 or 502, or are those different engines? Would they fit?

Again, I know it's pretty basic, but I just cannot seem to find an answer about this.

Thanks,

454 and 502 blocks(Mark IV, GenV and GenVI) are different but can use the same cranks, rods, heads, etc.
The Merc 496/8.1(Gen 7) is totally different.

As far as mounting the external dimensions are all the same and any will mount in the same place.

Big x bigger

Thank you :)

So if I wanted, I could drop in twin MR 700sci's? Would air scoops be necessary for the blowers to breathe, I wonder?

What drive?

nxt1?

That is good for the 700

A tall deck.motor will be different dimensions. 9.8 deck vs 10.2 . That is what you need to watch out for. Exhaust will line up different etc