For what its worth...the water pump on 2 gm and 3 gm
both raw and fresh water cooled that I have seen is
located behind the lower left pulley that we see in the picture...so very well may be add on...In any case bad to have leaking, a friend changing impellor for the first time
on his new boat had the screws rust from a leak and break.
Depending on how motor was maintained and run
(maintained and run hard is best, not babied)
motor could have a lot more life in it.