propulsion problem

[det352]

I have a 2000, Evinrude 70hp, 4 stroke. Recently have a problem with propulsion. Will be driving along and engine reeves (not hydroplanning), and loose propulsion. Trottle down and then back up and will continue along fine for awhile. I changed the prop. and experienced same problem. Seems only to occur at max. rpm., runs fine at 4500...

 

[Tim Frank]

Re: propulsion problem

I have a 2000, Evinrude 70hp, 4 stroke. Recently have a problem with propulsion. Will be driving along and engine reeves (not hydroplanning), and loose propulsion. Trottle down and then back up and will continue along fine for awhile. I changed the prop. and experienced same problem. Seems only to occur at max. rpm., runs fine at 4500...

If the prop that you swapped in was KNOWN TO BE GOOD, correct size, solid hub etc. all I can suggest is that you are boating in the Bermuda Triangle....
Seriously, I would be thinking that the prop is ventilating/dragging air. Your engine shaft/lower unit may not be quite long enough for your transom.....trim may be too high....or both. (some SAs may say that your transom is too high for the motor....)
Is the motor on a jack plate? If so, is there adjustment left to lower it?
Try one thing at a time so you know the solution.