Well I blew a head gasket and cracked the head and block. I came across a new 468 for 3000 bucks and sold the blown up stuff. I never saw top speed numbers with the 502 before it blew the head gasket. I hit 62 with a 29p prop, but was only turning like 4000 rpm with the 468. I am about to try a 25 mercury revolution 4 as soon as it warms up and I get my carb back. I am hoping to see 75mph.