is there a way to identify a merc 496 if it is a 375 hp or 425 hp other than by the pcm . i know that i don t have the correct pcm on my motor . i do have the serial # 0w695839

Should be a plate right on the heat exchanger that says if it is a HO or not. HO is 425, non HO is 375. At least that is where mine is.

your pcm should say h.o. on it.

Any Merc dealer can run the serial number and tell you exactly what it is.

the sounds of a Ho is lumpy and regular mag is smooth.

He is correct, My 496 sounds built, A little lumpy cam should be noticeable, when at idle. Where is your H.O. runs between 4600-5000 rpm for best HP and I think the 496 runs around 4600 rpm, If you look on the pcm looking at the front of the motor the pcm should be over the passenger side of the motor and mine says H.O. right on it.

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Op wrote

Also, the Engine # does not match anything @ http://www.mercurymarine.com/parts-a...parts-catalog/
You might want to get a better look at the engine # and do a search in the link above. There I am sure you can find out what engine spec you have.

thanks Micheal S but no luck it gives me both options