I have a Vetus 2cyl 10 hp diesel in a boat. Bad compresion on cly2. I took the head off and turned it upside down and poured gas over the valves. Only exhaust valve from cyl2 leaked through. The surface roughness in cly2 area and valves looked different, more " pitted". I poured oil into the open cylinders and no apparent seapage past rings after more then 2 hours. Can I assume the valve was the problem and not bother taking the rest of the engine out of the boat to do a ring job--a really big job?