Thanks Brian,

99% sure the guys above are correct but I have the same fitting on my Fountain. On my boat it is the filler for the fresh water tank! I know you've got a 496 vs my outboards but double check where the hose on the back goes to.

RR

My velocity has the same setup. It's a good idea when running the engine through the fresh water flush to block off the low water pickups in the outdrive. Mine has a dual pick up and I tape both shut up before starting the engine. The sea water pump primes much quicker with the lower taped off.