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1992 25 hp Powerhead

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Missourimerc

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I have a 92 25hp merc with what appears to be a bad powerhead. The bottom cylinder has 0 compression. In looking to replace the powerhead with another one i'm finding a lot that do not have the same part number. Just curious if another one of these powerheads would fit? My serial number is 0D093924 and my powerhead part number is 9533a3. I see mercurys from the middle 80's that have this same part number and some that don't. THe one i'm looking at which has good compression 135 on both cylinders part number is 9077A4 and the serial number of the engine is 0A911560. Wanting to see if I could put the 86 powerhead on my 92.

Thanks for the help!!
 
Yes it should interchange. Make sure the replacement powerhead has a thermostat like yours. 2 different powerheads made that yr. Also tell them to re-check the compression those usually pull about 120 for good compression because of the decompression holes.
 
flyingscott said:
Yes it should interchange. Make sure the replacement powerhead has a thermostat like yours. 2 different powerheads made that yr. Also tell them to re-check the compression those usually pull about 120 for good compression because of the decompression holes.
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Thanks flyingscott. Looks like both motors are from different serial groups. You can see from the diagram these are slightly different. You say the 86 will still work? 9077A4 Cylinder Block.jpg9533A Cylinder Block.jpg
 
Since they are not in the same serial group you need to double check the powerhead base gasket if that is the same then yes it will work.
 
Looks like the part number for the 86 powerhead gasket is 41670 and the 92 is 41670-4 but looks like part number replaced the old. So the 86 powerhead should work for my 92.
 
Missourimerc said:
Looks like the part number for the 86 powerhead gasket is 41670 and the 92 is 41670-4 but looks like part number replaced the old. So the 86 powerhead should work for my 92.
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The power head base gasket is the same for both 27-41670006. Do not buy the sierra gasket use the oem one only
 
When you get her running again,keep us posted with results, purchase a infrared thermo gun 20.00$ at harbor freight if concerned about running temperature.
 
Could it be possible that there is another issue with the 0 compression in the bottom cylinder? Most boat guys that ive talked to locally said more than likely that the cylinder is scored and not worth fixing.
 
There is no HEAD GASKET and no valves to worry about.-------------So yes it is an issue with the cylinder / piston condition.
 
I believe your 92 is a chrome bore. The only way to see if the bore is any good (short of tearing the motor down) is to take off the exhaust cover and the access covers. If the bore has not been damaged you can rebuild it BUT you have to use mercury pistons and rings. If the motor is a Mercosil block it can be bored out. I don't remember when they switched those motor to Mercosil.
 
New powerhead is on and motor will start. I'm guessing I have to sync the throttle cable? Motor starts and idles fine for a few seconds then dies when we put into gear.
 
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