I've never been over 66 in my 2017 Z19. First spring I had it I went to a lake with the boat empty except for 3/4 tank gas and the 36 volt trolling motor and one Power Pole Blade. Got 66. Kept hearing about everyone doing 68. Mid-summer found out the bolt that governs how far you can push the hot foot wasn't screwed in all the way limiting amount of throttle I could apply. Screwed it all the way in and still only got 66. Figured water was a lot warmer so no biggie. Next spring I added another Power Pole Blade, emptied the boat except 5/8 tank gas, batteries and trolling motor. Still got 66. Oh well...