Hi just bought à skater 36 without engines and are going to put in merc 600 sci and xr its before IT was 750 and imcos and à top speed of 134 how fast can it be whit the 600

120-125 maybe.

I would advise you NOT to put XR's on that boat. It is too big and you WILL break drives. I believe, that boat was actually built as a bravo boat and changed to #6. 600's will get you in the mid teens. 110-115

What he said ^^^^^^^

Say no, to Bravos of any flavor. # 6a is required, anything else is money wasted

No bravos on that boat unless you like walking on broken glass