Compression questions

[maisie]

I have a circa 2000 75hp Mercury 2 stroke engine.  I have tested the compression and it is approximately  82 and 85.  I have tried to find information as to what would be the correct compression for this outboard to no avail.  I was wondering if any of you would happen to know this?

 

 

Starts good, but smokes and runs rough.  any ideas?  

 

thanks for any input

[LongLine]

If you're using a screw-in gauge, I'd venture a guess you're running on the low end.  Most 2-strokes run 100+.  You may want to ask in the mercury section on I-boats.

 

Tom B.

(LongLine)

[Frogger]

Masie, from what little I know Tom is right typically they are higher, but I've also heard it's important that they are close like within 5% of each other. I'm assuming it has a lot of hours on the motor? Might be time for rings etc, but like what was suggested, someone else might have some suggestions

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[lakebound88]

I bet you should be upwords of 145 psi. I'm probably wrong but my 80's evinrude that was a 160hp had 145 psi on all cylinders.

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[maisie]

Thanks for the information Guys.  I think i might take the boat somewhere where i can get the compression done by a "professional" and see what's what.

 

Maisie

[RSF]

Do the same test with both plugs removed and record the results. THEN, do the same Only, squirt a couple squirts of two stroke oil in each cylinder first. If the compression jumps more than 15 pounds on either, Rings are worn. If the rings are worn you will lose power and flood the plugs causing it to smoke and misfire.