My boat motor sputter and shacks vibrates the whole boat when opened fully, and answers?

Question

It has no speed when this happens, but if you back off of it alittle bit then it runs fine. But it doesn't go very fast and it was before.

Answer 1

Get it tune up>

Answer 2

it's the prop it's time for a new wheel

Answer 3

I like all the answers-If you find nothing wrong with the prop shaft and the prop is true -undamaged and not slipping, you may have a cavitation problem.(All of the above can cause cavitation) Take a straight edge and lay it on the bottom of the boat just ahead of the lower unit. Is the hull flat just ahead of the engine? Next put the boat on the water and put a brave sailor in life vest to look down the transom and witness the formation of one or two mini tornadoes of air running down the back and into the prop. The first cure is to move the trim pin around and see if it will go away. The last desperate measure is install a "whale tail" or "Hydro fin" on the anti cavitation plate of the lower unit and try to intercept those tornadoes.---hope it's a bad prop.  

Answer 4

either an unbalanced prop, or a bent shaft.

when this happens the harmonics of the prop are off, and all the rotations with wobble are cancelled out, a lot of turbulence occurs, and no forward momentum is achieved.

Answer 5

Maybe your prop is out of balance or damaged.