is the motor setting level or up a little?does it have power trim?sounds like it may need tucked under,if you don't have power trim there is a pin in the transom braket you can pull out to let the motor down,that is all you may need to do,is the prop eat up bad or bent?you should not need a xtra long shaft motor,i assume it is a flat bottom if so as long as the prop is under water they will usuall just flatly scoot off,if it don't work you may need to invest in a set back plate.