is compression 105/135/125 BAD, running rough

[jc60merc]

My 1986 60hp Merc losted power and now runs very rough. Idles a little rough, but really starts missing under load and will not come up on plain.<br />Checked compression 105/135/125 top to bottom, seems to have good spark on all plugs. Rebuilt both carbs and didn't find anything wrong.<br />Can these compression reading be telling me something is broke internally? and could this be the source of the miss or would it just be down on power a little?

 

[The Marine Doctor]

Re: is compression 105/135/125 BAD, running rough

You most likely have a broken ring on the lowest cyl. And quite a bit of wear on the others.<br /><br />on the Starboard "Right" side you can remove the intake Do not confuse this with the part behind the carbs.<br /><br /> It should be the large plate under the electronics with fins. Runs the length of the powerhead.<br /><br />Remove this plate...you can then see the pistons.<br /><br />TMD

 

[roscoe]

Re: is compression 105/135/125 BAD, running rough

Is the top sparkplug cleaner than the others? Perhaps running lean. Perhaps a head gasket leak. Comp on #1 is too far out of line from other 2.