I picked up an old 1971 Formula with a Mercruiser 165 for free from a guy on Craigslist. There are a bunch of parts I could use off of it. The fresh water cooling system was a good find. The hull is in good shape and it would be a shame to junk it without trying to fix the engine. Compression is 1- 70psi , 2-120psi , 3-150psi , 4- 5psi , 5-140psi , 6-140psi. The cylinder head is pulled now and the all six exhaust valves are recessed but are not burnt. Intakes all look good. No scoring in the cylinders and can still see cross hatch from honing. No thick ridge from cylinder wear. The exhaust valve on cyl 1 &4 are def leaky. Light can be seen through the valve/seat while shining light in port. Nothing big. Just a tiny little crack of light that can just barely be seen in a very dark room(only around 1/4 inch long). The owner believes he's been running without cyl 4 firing since he bought it 5 years ago. I was expecting burnt exhaust valves on cyl 1 & 4. Especially 4....maybe even a hole in piston 4. I'm not sure what is causing such a loss of compression . Had heads off on other engines before and damage was obvious. Not sure here. The exhaust valves are recessed about the same on all cylinders and the bottom of the valves are flush with the head. Can anyone offer how to proceed ? I'm not sure what is causing the compression to be so low on cyl 4. Are the exhaust valves the problem? Should I have adjusted the valves before pulling the head?
