Merc carbed 225s: Difference beteween 225, 225 Marathon and 225 SeaPro?

[gw204]

Just bought a '96 Robalo walkaround with a carbed 225 Merc (SN 0G350827). Looking up that SN on Merc's parts site gives me the following model to choose from:

225 (3.0 CARB)
225 MARATHON (3.0 CARB)
225 SEAPRO (3.0 CARB)

Does anyone know what the difference between these three is? Just want to be sure I'm selecting the correct model when I go to gather part numbers.

Thanks.

[gotboostedvr6]

First one.

1st thing I would do is drop the lower and see how many splines the drive shaft has. Some 96 have 8 some 13.