anyone have top speeds on this model boat with twin 502's or 500's in them .

I only know of one running 500's but they have pro chargers on them!!!!run's mid to upper 80's

Depending on load/equipment, fuel & water conditions... average 42 with 500's will run 70mph or so. Maybe a little more in rougher water, less hull in the water. I know mine gets a little faster in bigger water 3ft or so compared to 1 & 2's. I have ran in 4-5ft very comfortably at 50mph with very little disturbance or pounding the hull when trimmed & tabbed properly. They just eat up the big water. There are faster boats out there than the 42 Sonic of comparable size, but few will give the ride comfort in the big stuff. It's all in what you want !!!!

New 42's with 575's & boxes will run upper 70's close to 80, with standard equipment. Local dealer had a newer model 45 with 3- 575's, and she ran 86-88 on GPS. Currently for sale with low hours on trailer, for $275k or so. Good deal...clean boat, however interior/vinyl colors was ugly as hell !

Forgot...... check back 30 or so days ago in the Sonic forum, I had asked similar questions for comparison.
BTW- Up north somewhere there is/was a 41SS with big naturally aspirated big cubic inch engines that ran over 100mph !
Put the power in them and they will run !