Grey foamy substance out of propeller exhaust

[spareparts]

find a diagram that shows the crank and the case halves, look at the very bottom, it has a seal carrier, just below the bottom bearing
item # 30 on this page http://www.butlermarineinc.com/fiche...r=0&fveh=50024

you may be able to drop the lower unit and inspect it with a light from the bottom end, spin the motor over while you have the lower off, you may be able to see crank case pressure bleeding by the seal