Re: 86' mercruiser 170. Low compression in one cylinder
Can't really say, but when I did mine I spent about $450, but that includes a complete valve job, hardened seats and replacing a couple of valves. For a head gasket only, the parts will you about $70. The labor is where the expense is, and I do not know how many hours it will take. The engine does not have to come out. It is not a terribly hard job, and any good mechanic should be able to do it, just have to be sure to follow the instructions in the manual. Try the compression with the added oil. If it comes up significantly there is a chance it is the rings (don't get your hopes up) and you could probably run it, if not it is probably the gasket or a valve and I would not run it because it will only get worse and could do some damage. Yeah it is a bummer, but if you get it running well it is a pretty good motor and you should get years of service out of it. As for mechanical ability, you would be surprised how easy some of this stuff is. Read the manual over a few times so you will understand what needs to be done, that way you will be better informed if you take it to a mechanic. The encouraging thing is the other compression numbers are great which is a good sign. Good luck.
