I just purchased a used 16 ft flat bottom boat with a Vanguard 35HP longtail. I do not know much about it but learning each time I go out. PROBLEM. I takes everything i ve got to keep the tail/prop in the water. When under load it just wants to come out. Is the motor set up correctly? I watched many videos on YouTube of what looks to be the same set up and the videos show the guys flying around with no effort keeping the prop in the water. HELP!

What's your transom height? What's your shaft length? What brand is your unit?

Might be somthing as simple as adjusting your cavitation plate, or could be wrong combo of transom height/shaft.

If it's a GD, the owners manual on their website has instructions on how to adjust with a crescent wrench. What speeds are you getting WOT when your prop is fully submerged? Ideally you want the cavitation plate to be just below the surface.

Search google with "mudmotortalk cavitation plate" or use the search bar. This has been discussed a lot.