I'm looking to buy a warranty 7.4 Merc horizon.It's been imported here as is and complete.Looks like it's done little or no work at all.When the engine importers ran it they are telling me the sump was being pressurized.What could this possibly be?I don't know much about the Horizon series.Were they anything special?Any information greatly appreciated.

That would indicate excessive blow by past the rings. They are just like any other engine in that respect. I suspect the engine has real problems unless the pressurization was fairly minor.