can't find my serial number

[james__12345]

I'm working on a mariner for a friend of mine and can't find the serial number I'm finding listed in any parts list. The number on the plug in the block is 578877. On the plate on the bracket it has 6a3 printed and the 558877 cut in. The hood says its a 50, but its only a 2 cylinder, but I'm not sure if its a 50 because the 50s I'm finding are 3 cyliners. Can anyone point me in the right direction?

 

[Fun Times]

The number on the plug in the block is 578877.

This number is coming up as an MARINER SANSHIN 55 ML - ( 55 H.P. (1984) Serial No: 578877 Model No: 7055324 Parts Catalog No: 90-95612

On the plate on the bracket it has 6a3 printed and the 558877 cut in. The hood says its a 50, but its only a 2 cylinder, but I'm not sure if its a 50 because the 50s I'm finding are 3 cyliners. Can anyone point me in the right direction?

Are you sure it's an A and not an 6 ? I can't seem to locate any 6A3 numbers just an 663 number under the 55 HP which would help confirm the engine to be a 55 H.P.

Also 558877 is coming up as Serial Number not found on the computer system.

Here's your parts catalog for the engine model that's coming up. http://www.mercruiserparts.com/selectDocs.asp?doc_nbr=95695

 

[james__12345]

Yes, its an a and yes, its a 55

 

[james__12345]

I just noticed I had the number wrong the second time. It is 578877

 

[james__12345]

This is the plate. Any chance that it's a misprint and that is the right parts list?