79 black max .. ???

coolbikeguy

Chief Petty Officer
Joined
May 14, 2009
Messages
491
looking at a 79 merc black max v6 150 hp. were these good engines ?? have any known issues ? i was told that the mercs do not have a removable cylinder head so if it would ever need bored it may be hard to find a shop to do the work because of boring a blind hole. any comments on that ? also what should the compression be in this motor ? thanks guys, scott
 

prolinews

Petty Officer 2nd Class
Joined
Feb 1, 2005
Messages
165
Re: 79 black max .. ???

does it have head bolts? It can be bored out, the v6 merc is a great motor 2.0 2.4 2.5 most parts are interchangable and available at most parts stores they are proably the most inexpensive motor to work on.
 

prolinews

Petty Officer 2nd Class
Joined
Feb 1, 2005
Messages
165
Re: 79 black max .. ???

compression should fall between 110 and 135. the blind holes are on later model engines. I would check the compression cold and then hot . I don't have the tools to do a leak down so a weak cylinder will usually show it self cold . Some engines that check even hot will leak down . If it shows good at cold it will be good at hot . What I'm trying to say is that some times a hot engine will hide worn rings where a cold engine won't . I hope this makes some kind of sense.
 
Joined
Aug 27, 2009
Messages
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Re: 79 black max .. ???

this was a great engine in its day. after checking compression, spark, gear oil, ect take a good look at the engine wiring. we see a lot of corrosion/broken wires. alsotake a look at the trim hoses, make sure it has the lower mounting bolts that attatch the trim hoses. last time i checked they were hard to come by. another problem these engines had were the recurculating check valves in the intake. they are really easy to change but will cause a major idleing problem if not serviced.
 

coolbikeguy

Chief Petty Officer
Joined
May 14, 2009
Messages
491
Re: 79 black max .. ???

thanks for the info guys. i havent seen the motor in person yet but will take all this info with me of go this route. scott
 
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