How much do boat mechanics cost to evaluate a potential used boat purchase?

Also is this common for the used boat purchaser to hire a mechanic to look at the prospective boat before purchase? or would a boat surveyor only suffice? Do boat dealers expect a buyer to hire their own mechanic or do dealers roll their eyes at this type of request?How much do boat mechanics cost to evaluate a potential used boat purchase?
Most Surveyors only survey do not tell U of potential problems .U could have unless it broken or not working . My self as Mobile marine repair, Will come aboard and fine issues that will need attention now or in the near future. Dealers want U to except there word as it was only used by a little old lady on sunday to go to the floating services around the corner. Between $80 %26amp; $100 Per hour. For Service %26amp; repair Florida Keys.