This is related to my post on excessive vibration. When removing the shaft to replace the cutlass bearing, the boat yard noticed that the shaft did not line up with the hole in the rudder that enabled removing the shaft without dropping the rudder. There was also a 12" circle of different colored gel coat in the engine compartment above about where the end of the skeg would be, indicating some sort of repair. No one brought this up at time of survey ( I should have in hindsight). In checking the PO's repair receipts, I found a line item that read 'modify keel and add lip to tunnel'. The cost was about $1000. Any idea on why they would want to make this modification? What condition were they hoping to fix? Is this a common modification on MS Pilot single engined boats? Thanks for any insights. Sammy