15 Merc late 90s foamy oil out exhaust dont think lower unit any ideas

[Evinrude200]

Late 90s 15 merc 2 stroke just purchased there is foamy oil coming out the exhaust wondering what might be cause not really sure where to start. I dont think this is from the lower unit lube can see it all back in exhaust. Head gasket, cylinders, rings, thinking start with pressure test or am i looking in wrong direction.

Any ideas would be greatly appreciated thanks