1986 merc black max 200hp

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salted rim

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Trying to find out if compression is ok #1has 115 #3 has 118 #5 has 115 #2 has 115 #4 has 115 #6 has 111 all testing was done with plugs in except where tester was at and did not warm engine up prior to test how close is this to spec ? thanks for the help
 
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eh350x

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Re: 1986 merc black max 200hp

should be in the 130 range ,I have saw them run on some low readings similar to yours
 
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salted rim

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Re: 1986 merc black max 200hp

thanks eh350x so this would be considered low compression for a 200hp black max
 
j_martin

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Re: 1986 merc black max 200hp

Did you prop the throttle open? (screwdriver handle between the throttle roller and cam)

Also, I usually pull all the plugs and let them free wheel except for the one I'm gauging.
 
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salted rim

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Re: 1986 merc black max 200hp

no i did'nt had 3 mech tell me #s were ok had one mech say they should be 135 to 140 psi so you can see why im concerned just trying to find out what the original specs were , motor runs good, thanks admiral
 
j_martin

j_martin

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Re: 1986 merc black max 200hp

salted rim said:
no i did'nt had 3 mech tell me #s were ok had one mech say they should be 135 to 140 psi so you can see why im concerned just trying to find out what the original specs were , motor runs good, thanks admiral
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I'd look at your compression gauge with a jaundiced eye.

Even is more important than absolute numbers. I suspect you'd get a bit more with the throttle propped also.
 
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salted rim

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Re: 1986 merc black max 200hp

i'll try that also i'm going to pull the plugs so it can freewheel would you suggest warming the engine prior to testing ? Would you consider these #s low or medium , good ,bad ? Thank you
 
j_martin

j_martin

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Re: 1986 merc black max 200hp

salted rim said:
i'll try that also i'm going to pull the plugs so it can freewheel would you suggest warming the engine prior to testing ? Would you consider these #s low or medium , good ,bad ? Thank you
Click to expand...

If it runs good, especially idles good, I'd have the compression gauge checked.
 
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