I've got a 2000 Volvo Penta SX 5.0 with a bad lower unit. I've been looking for replacement lower units. I've verified the gear ratio is 1.60 as listed on the serial number plate on the upper unit. I found a complete replacement lower unit with the 1.60 ratio, but its from a 1999 boat. How can I verify this would be compatable with my 2000 boat? Thanks.