"Sal: I looked up the engine
"Sal: I looked up the engine diagram and the valve cover does not show a PCV valve in it which is supposed to vent blow-by gases back through the carb. If the PCV valve would plug shut w/sludge, then the gases would build up enough pressure to blow the oil out of the dip stick or valve cover gasket or in your case the valve cover vent hose.
Blow-by gases from combustion "blow by" the worn rings down into the crankcase block and have to escape due to the increased pressure so they take the path of least resistance--thru the closest piston with worn rings and into the head and valve cover or up through the oil return journals causing the "oil spitting". BB gases can also travel into the valve cover thru worn Valve Guides and VG seals, and even if the VG seals are new.
The "spitting oil" leads me to think that you have a problem with at least one cylinder causing the spitting as the cylinder fires. You have either worn valve guides and seals, a warped head surface or a warped block face or worn piston rings. Did you check the surface of the head and the block with a straight edge for warpage. That would cause blow-by gases to enter the valve cover via the leak caused by a worn valve guide, warped head or block face.
Does the engine idle smoothly? Any backfiring means a burnt valve or warped head allowing hot gases to reach an adjacent cylinder. What do the plugs look like? They all should be light brown w/out any oil fouling if the engine cylinder compression and combustion is correct in each cylinder. Since it did get HOT "overheat", the above warpage may exist or the rings in one or more cylinders are shot.
Do the dry/wet compression test and it will tell you what is wrong. If you have closed cooling, an exhaust gas anylizer would tell you if the head gasket failed again due to warpage.
Use a vacuum gauge and follow the directions on how to interpret what the gauge is telling you. Your engine should pull 18-22" of vacuum at idle and the gauge needle should not be jumping around. The jumping around indicates several problems which are explained in the instructions or the boat engine manual.
Also connect an oil pressure test gauge directly to the engine and get an accurate pressure reading. Low oil pressure would indicate worn engine bearings from the overheating and/or a failing oil pump.
Overheating the engine for a minute can destroy the rings and main bearings. My straight 6 Ford Mustang overheated back in 1970 on the interstate in Tenn. The engine would start but had no power. I watched them dismantle the engine. When each piston was pulled, the rings fell off in pieces. It doesn't take much heat to ruin the bearings either. When the crank was pulled, the main crank bearings were melted flat from the intense heat.
Your engine is 21 years old. It can't run forever without parts wearing out. I think the overheating did more damage than you think. If the tests for compression and oil pressure show failing rings and bearings, bite the bullet and repower. It will put you back on the water for a long time w/o more failing parts.
I hope I gave you some insight where to look. It has to be warpage and/or rings. Let me know what you find. Guy"
