7.5 vs 9.8 block

A

Aaron Lariscy

Seaman Apprentice
Joined
Apr 23, 2011
Messages
33
What's the difference between the two blocks of the same year I am thinking about swapping but need to know if its compatable. I have crossed the powerhead to foot gasket and he crankshaft and they both check out but what gives it 2.3 more HP?
 
79Merc80

79Merc80

Senior Chief Petty Officer
Joined
Nov 22, 2007
Messages
673
Re: 7.5 vs 9.8 block

Port timing, is likely the only difference. Placment and size of the intake and exhaust ports
 
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