Just bought a set of used skis, one is '89 Kawi 550. It seems to run fine on the water under a load but when it comes out of the water and revs up, there is a heavy vibration felt all the way in the back. Very prominent when hitting high RPMs, not so noticeable when its under a load. Haven't had a chance to crack into the ski yet but wanted to get a head start on what I might look at first. The PO had a replacement motor installed by a mechanic and it hasnt been ridden since it went in. Engine alignment looks good but havent actually measured it. Any info on where to start looking would be great.