I have a new to me '81 Mercruiser 228 5.0L. The dipstick tube has a
threaded fitting for a hose attachement that, I think, is there to suck
the oil out. I don't know if there is a plug on the oil pan or not.
I'd either have to remove my whole rear seat (possibly openning a huge
can of worms) or stand on my head in the engine compartment to find
out.

I know that they make hand pumps to get the oil out but I want to do is
hook up a hose to the dip stick tube with the other end lower than the
engine (in a bucket on the ground). Instead of needing a pump or
sucking on the hose to get a siphon started, I was wondering if I might
be able to apply a VERY SMALL amount of air pressure to the crankcase
to get it started. I'd do this probably through the PCV fitting. When
I say VERY SMALL, I mean like 2 or 3 psi. Just enough to get the flow
started. I would increase the pressure in very small doses if 2 or 3
was too little. A dumbass would apply 40 psi and blow out a seal or
gasket. I may be dumb but not that dumb. Can anybody tell me if this
will work or if there are any problems with it?

Chris