How fast would a 02' Sonic with a pair of 496's go? Also what would it take to get it up to 78-80mph?

Not a chance! A 31ss with 496 MAG. HO's only went 76 in a magazine test article. The average boater in this fourm are usually seeing 74mph in a 31ss. They have more fuel and items on the boat. I would guess right a 70 maybe.

Raylar kits!

Probably run around 70, I would think it would need 575's to make it to 80.

I run a 2002 35' 358 Diablo with 575sci's....... when I 1st bought the boat I would hit 79mph no problem but couldn't seem to get 80mph. Last winter I rebuilt the both engines to stock specs (550hp at the prop)..... I purchased a new set of props and was still running 79mph..... The last run of last season I was in a poker run....... I damaged the new props the night before the run so I put my old set back on the boat......... Lo and behold I was running 82-83mph........ Since the season has ended I sent my props to BBlades and explained my situation...... Bret said the props that were running 82-83 are basicly all over the place with dimensions and really have no meat left to repair.... he also said the props that are damaged can be fixed and modified..... with out making any promises Bret said I should see a mile or two per hour more then I was with the beat up old props......... sorry to be long winded but I am hoping to see 84-85 next season........ My guess for a 496 powered boat would be about 71-73mph....... just might be working hard to do it.......