I have a 94' Mercruiser V8 350 engine , it's extremely difficult to
start, I usually have to put it in neutral and pump/push it forward and
back maybe 5 times then almost put the throttle all the way forward for
it
to start (and still it has to crank for a about 5 seconds before it
starts), once started i run it at maybe 2000rpm for a minute or two then
I
can put it back to idle and no problem. If I let it run for a while the
next time i go to start it, it turns over perfectly.... Now when I put
it
in the water an hour or two later, i have the same problem except it is
magnified and more difficult to start.

I have the same problem with my '95 4.3L 4bbl Mercrusier. I think the
problem is that the carb allows the fuel to leak out while sitting. The
electric fuel pump on mine is connected to power via an oil-pressure safety
switch, which means that the carb doesn't get any new fuel until you start
cranking the engine and the oil pressure comes up enough to activate the
pressure switch and turn on the electric fuel pump, which then starts
filling the carb bowl. The accellerator pump works, so I pump the throttle
10-15 times to shorten the cranking time. Another thing I did was to run
another switched power line to my fuel pump that I can use to turn on the
fuel pump before I crank the engine. The pump gets it's power from a lug on
the coil on mine.