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Old 07-17-2015, 08:53 PM
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Default 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,
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Old 07-18-2015, 01:38 AM
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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.
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Old 07-18-2015, 05:13 AM
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Big x bigger
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Old 07-18-2015, 08:36 AM
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Originally Posted by Griff
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.
Thank you
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Old 07-18-2015, 10:33 PM
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So if I wanted, I could drop in twin MR 700sci's? Would air scoops be necessary for the blowers to breathe, I wonder?
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Old 07-19-2015, 07:34 AM
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What drive?
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Old 07-19-2015, 02:20 PM
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Originally Posted by waybomb
what drive?
nxt1?
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Old 07-19-2015, 03:17 PM
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That is good for the 700
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Old 07-19-2015, 05:47 PM
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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
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