I have never owned a I/O before and am cosidering a 18 ft. Cobia Bowrider with a 1991 mercruiser 3.0 and Alpha one out drive. The Head has been redone,carb rebuilt,new elbow,and manifolds. Work has been done by a dealer. What is considered a good pressure rating for a compression test on an inboard?Anything I should check out on the outdrive other than the oil? Any suggestions or advice appreciated.