Lower Unit Assy.

I need to replace the lower unit on my 1991 200TXRP,there are two listings in the parts section.6G5-45300-23-EK and 6G5-45300-13-EK,can someone tell me which is the correct unit for my engine.I know there is a unit with a longer drive shaft.How can I tell which one I have.

Thank you

[boats.net]

You will need 6G5-45300-23-EK it's for the 25 inch shaft motor, the -13 is for 20 inch shaft.