1986 merc black max 200hp

[salted rim]

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

 

[eh350x]

Re: 1986 merc black max 200hp

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

 

[salted rim]

Re: 1986 merc black max 200hp

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

 

[j_martin]

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.

 

[salted rim]

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]

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

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.

 

[salted rim]

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]

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

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