Watch it, old man. I weigh over 300 ... but not for much longer, as I'm still dieting and losing steadily. Down 100 pounds from a high of 430 two years ago. And even with every storage box stuffed full and my life partner onboard, our Ranger Z-119 will do 68 (GPS speed) in the right conditions. It's done 70 in the past with less gear onboard.
However, with that said, I rarely run that hard, even in a derby. You have to push it hard at takeoff or you'll get run over. But after that initial run, I rare push it over 4700-4800 RPMs, as that's where my Pro-XS 225 likes to settle in and purr. Just not worth the safety risks, not to mention unnecessary wear and tear on our rig.
Being primarily a "winder" vs. a "dragger," my total number of casts for a day's fishing is probably going to approach 1,000. If I can't catch a good sack in that number of casts, risking life and limb to squeeze in a few more ain't gonna make any difference.