3.0 head gasket replace tricks

[airshot]

I am going to replace the head gasket on my 1983 3.0 mercruiser 140 hp. I do have the merc shop manual and have worked on cars many times. Have also done all my own maintenance on this boat since I have owned it. I have a lower compression on 2-3 by about 30/40 lbs and am beginng to hear a puffing sound when starting and shutting it down. No oil consumption other than main seals, no water in oil and runs great other than it is developing a rough idle and wants to load up at idle, so I figure to fix this before things get worse. SO.....what I am looking for is...does anyone of you more experienced mechanics have any tricks, tips, suggestions or recommendations on things to watch out for to make this job go much easier? I was planning on doing the intake gaskets as well...sort of a go thru everything while I have it apart. Any and all information will be greatly appreciated..thanks in advance .

 

[Scott Danforth]

Easy job. Pull intake and exhaust. Pull valve cover, pull head. Clean, New gaskets, install

 

[airshot]

Didn't figure it was to bad, after going thru all that work I think I might as well send the head out to have the valves reseated and check for flatness. If I were thirty years younger it would be a piece of cake, but at my age it is more like a piece of concrete.

 

[Alumarine]

Didn't figure it was to bad, after going thru all that work I think I might as well send the head out to have the valves reseated and check for flatness. If I were thirty years younger it would be a piece of cake, but at my age it is more like a piece of concrete.

Good idea to get the head checked out while it's off. It's not that expensive.
When my glaston was about 30 years old I had the head checked and the shop said it was just fine and to leave it.

 

[Fishermark]

Put a little oil in the cylinders and do the compression check again. If it raises the compression, then the chances are good you have ring issues. If it does not, then you may only have the valve or head gasket problem. If it turns out to be rings, then you are wasting money on a head gasket and valve job.

 

[airshot]

Put a little oil in the cylinders and do the compression check again. If it raises the compression, then the chances are good you have ring issues. If it does not, then you may only have the valve or head gasket problem. If it turns out to be rings, then you are wasting money on a head gasket and valve job.

Thanks for the heads up, however I did that in the spring and it only changed it a couple pounds. Having only the 2-3 cylinder low and hearing the puffing sound makes me believe it is the head gasket or possibly burnt valve. I am going to check the cylinders when I get it apart.

 

[Bondo]

Having only the 2-3 cylinder low and hearing the puffing sound makes me believe it is the head gasket or possibly burnt valve.

Ayuh,.... If it's blown 'tween 2, 'n 3, it could have erroded the head, or block, where the blow out is,....

Check it closely with a straight edge,...

 

[airshot]

Yes Bondo I certainly will....as a tool maker for more than 45 yrs I am well versed on checking flatness. Also considering a possible burnt valve (valves). Got to take her apart to see.......She just ran so good I hated to mess with her, but towards the end of the season the idle became rough, the puffing sound became noticible and it wants to load up if she idles very long....and not from running rich.

 

[harleyman1975]

I would have at it. I agree with the head/gasket being the most likely culprit. pull head, check both bock and head for true, put some acetone in combustion cambers to check for leaking valves and if all good then put her back together.

 

[airshot]

I would have at it. I agree with the head/gasket being the most likely culprit. pull head, check both bock and head for true, put some acetone in combustion cambers to check for leaking valves and if all good then put her back together.

That is my plan, want to take a good look at valves while it is apart, if any question at all I plan on sending it out and get the head gone thru. No sense putting it back together then having to do it again. Figure to spend the money and get it all done at once, Thanks for all the tips and notes....just trying to be sure I have all my bases covered before I start this job.