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1988 mercruiser 30 a bad nightmare

kingc560

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"i have low compression on 2cy

"i have low compression on 2cylinders #1 135, #2 130, #3 50 #4 75. could this be a bad head gasket since the bad cylinders are next to each other or is it a bad , cracked head. where should i start looking first? any info would be great. thanks for your time."
 
these reading were with all th

these reading were with all the plugs out?
could try injecting compressed air into 3 and see if you hear it in 4
a little oil in the cylinder and redo the compression test
leakdown test : air out the exaust: exaust valve
out the carb: intake valve
out the valve cover: rings
 
Bt Dr. is right. A few boater

Bt Dr. is right. A few boaters have found a small crack in the head gasket w/those symptoms.
 
"well,i took the head off toda

"well,i took the head off today. the gasket looked ok but the head looked terible. the head were covered in rust in the 2 that had low compression.is this a cracked head? i have a good head off a merc 120 2.5 will this worked. the piston and cylinder walls looked good. wierd? i would like to thank everyone who has helped me. i have no money and just trying to get on the water with my kids"
 
""head were covered in rus

""head were covered in rust in the 2 that had low compression.is this a cracked head?"

Water intrusion caused the rust. Why? What did the exhaust manifold gasket look like? My guess is a bad gasket, cracked exhaust manifold, cracked head or cracked block."
 
"possible rusted valve seats??

"possible rusted valve seats??

Maybe burned valves???
I just burned up two exhaust valves on my 3.0L last week. Sucked!!!! But now shes back together and brand new!!! Goodluck. Keep us informed...
286648.jpg
burned exhaust valve #2."">
286649.jpg
286650.jpg
After rebuild
 
"Dan,...
Until you figure out


"Dan,...
Until you figure out to post pictures,...

Don't....

You're screwing up these threads,...
Making them Unreadable..."
 
"There is a 2 part kit availab

"There is a 2 part kit available to check for cracks in the surfaces of heads and blocks. Clean off the crud, spray one part on and wipe it off. Spray the next part on and wipe it off and the cracks will stand out like a cracked window."
 
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