Trying to winterize a 1991 Mercury outboard. I hooked up a pair of
universal flush ear muffs to the engine water intake and turned on the
hose. Water was spitting out of a couple places in the lower unit
before I started the engine. When I started the engine water still
flowed out of the lower unit but no water came out of the water
discharge hole which is mounted on the rear of the engine itself about
half way up. I turned off the engine and tried blowing through the
water outlet and was able to blow through it easy so I repositioned
the flush muffs and tried again, to no avail, water was flowing freely
out of the prop though. I never let it run for more then 10 seconds
and the engine remained cold to the touch. When I turned off the water
I was able to hear water trickling down out of the upper drive unit. I
searched the net but couldn't find any info. Shouldn't water come out
of this hole the same is if it were in a lake? If so what should I
look for? Please help.

George