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1990 Mercury mariner 175hp motors locked up

B

Bass addict

New member
So I have a 1990 Mercury mariner 175 hp motor that's locked up. I have taken off the lower unit and its fine. I pulled the plugs and there's no trace of water anywhere. I than took off the valve covers and exhaust manifold. I couldn't find a failure with the Pistons or cylinder walls. One of the Pistons feels a little loose but other than that everything seems to be ok. You can turn the motor by hand but it stops once you reach a certain position and then u can turn it back so far before it stops again. I'm assuming it's a crank or timing chain problem. I don't feel comfortable tearing down the motor any further and I'm afraid that if I pay a mechanic to finish tearing it down to diagnose it, he might tell me the motors screwed and I'm out a couple hundred dollars. If it's a simple repair should I rebuild anyway? Any advise or thoughts will be appreciated. Hopefully by my description someone can tell me what's wrong. Thanks to all that can help.
 
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Is it a 2 stroke or 4 stroke motor ?-------------Serial # ?------Are you mixing gas and oil ?-------Is it oil injected ?---------Oil injection checked if it has that ?
 
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2 stroke and boats at my buddies place don't have serial # on hand. Oil injected and haven't checked the oil injection pump if that's what ur asking
 
You may be right. When the motor shut off the sound it made was similar to what I heard when the timing chain broke on one of my cars.
 
Sounds like you've had a crankshaft bearing failure. No two ways about it, the powerhead will have to be removed and disassembled for inspection.
 
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