Mercruiser Identification

25thmustang

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I assume someone will be able to help, but I am coming up without any 100% confident answer.

I purchased a used 1986 Cruisers Inc 26 Holiday that I am 100% sure had a repower done (from an OMC to a Mercruiser). The engine is closed cooling and on top of the heat exchanger it says 350 MAG. I assumed it was some variation of a 350 (260 hp). It has an Edelbrock intake and carb, which is not a factory set up. On the back of the block it is stamped GM57L, which online some say could mean 5.7, others state it could be a 5.0 or 5.7.

The Mercruiser serial number on the other side of the block near the starter says B964840 (I assume it is 0B964840 without the first 0). I have typed this in to a couple we pages that deal in Mercruiser. Mercruiser Parts says 200hp 5.0L (2bbl), however under that it says 200/5.0L/LX 260/5.7L MAG Alpha... with that said, the serial number range for this engine ends with 0B774444, whereas mine is a higher number.

Another web page gives ranges of engines and mine could fall into a few categories, from
 

Bondo

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Ayuh,.... Sounds like ya got a 350 Chevy, probably 'round 260 to 300 hp,....
 

25thmustang

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If it’s a 350 Mag, it built with the 5.7L GM block, which sounds consistent with what you found.
I assumed it was a 350 and the closed cooling set up came off some 350 "MAG" engine, however the fact that a couple websites say 200 hp 5.0 (305) when I type my serial number in, now I'm uncertain. If it runs well and doesn't struggle, I guess it doesn't truly matter, however I always like to know what I have (for parts purchasing and resale).
 

Fun Times

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25thmustang

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Comes up as an 1987/88 MERCRUISER MAGNUM W/ PS 350 ALPHA Model number 4350100AS..., https://www.mercruiserparts.com/200-2-bbl-gm-305-v-8-1987-0b525982
I clicked on your link and this is one of the pages where it seems to indicate a 200hp 5.0L 2bbl engine.
 

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