Try looking up the part in BAM's site. Great place to deal with too.

http://www.mercruiserparts.com/selec....asp?type_id=8

If you just changed the plugs i would pull them all out and check and see if you cracked one.. had same issue and i cracked one of of pita plugs on the outside.if its cracked it will have black line in the white part of the plug..

also make sure the gaps are right may have squished one down alittle

Thanks for all the replies. .plugs look good..runs and sounds great on hose..how many fuel pumps are on this engine..ive only found one on the side by the canister filter..this motor is before the cool fuel...looked up pump by serial # on BAMs site and its the same part # but every where I look it says its for a carb motor..these are early serial# motors..when u look up by part # it says its a low pressure pump 10-15psi..am I missing something here. . Doesn't seem to be enough psi for efi...but damn if I see another pump..

Some searching gave me this,

496 Mag & HO 496/ V-8 2001 - 2004 (0M025000-0W059999) 861156A03 (2) 861155A3 (1) N/A

Found that from here:
http://www.sterndrives.com/fuelpumps.html

Your fuel rails probably rusted on the inside and one or more of your injectors is clogged. GM made a "plated" rail in the later years so look into that. Could also be crank sensor but with yours being an early model 496 I'd say put a fuel pressure gauge on that schrader valve and watch your fuel pressure. Your rail is probably nasty....

Crank sensor generally throws codes.