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Mercury 525 EFI 502 CID

Old 08-19-2021, 02:26 PM
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Question Mercury 525 EFI 502 CID

I have 2 of the Mercury 525 EFI 502 CID engines I am trying to rebuild. I cannot find the serial number or model of engine in the specs label it is either gone or never been printed on it. I am trying to figure out which exact model and year the engine is to order parts for it. The Block has the numbers C272, C12561358. The cylinder head has the number 900 843425. The Intake: 12550669. The pistons have the number 843302A1. Would appreciate any help. Are there even parts available for it anymore?

Model: HP525 EFI
Displacement: 502 C.I.D.
Max WOT RPM: 4800-5200
Spark Plugs: NGK BPR6ES
Spark Timing: Non Adjustable
Fuel Octane: 87(R+M)/2 or 92 Ron International
Engine Oil: Mercury/MerCruiser 4-Cycle 25W40
Engine Coolant: Dex-Cool


Thanks
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Old 08-19-2021, 02:44 PM
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look on the block where the heat exchanger bolts up, I found these on Merc 500 EFI's

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Old 08-19-2021, 03:01 PM
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Should be a label right on the left side of the heat exchanger if you were looking at the front of the motor. May be another on on the back of the motor somewhere but not sure, I might be thinking of the transom assembly.
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Old 08-19-2021, 04:21 PM
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Originally Posted by IGetWet View Post
Should be a label right on the left side of the heat exchanger if you were looking at the front of the motor. May be another on on the back of the motor somewhere but not sure, I might be thinking of the transom assembly.
That label is unclear due to corrosion unfortunately right on the side that says the engine serial number any other way ?
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Old 08-19-2021, 06:02 PM
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There are only a few minor changes in all the 525EFI's and nearly all parts are the same.
https://www.mercruiserparts.com/525-efi
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Old 08-19-2021, 07:23 PM
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Quick search: Block is gen vi. Pistons are made by wiseco for merc racing.
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Old 08-19-2021, 07:25 PM
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Originally Posted by Griff View Post
There are only a few minor changes in all the 525EFI's and nearly all parts are the same.
Great thanks! I think I found the model # itís barely visible but I think itís 0M900180 so should be the first set on the parts page.
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