mercruiser 3/0 Ignition?

[Boat Doctor1]

1999 merc 3.0 chev 4 cyl. with solid state factory ignition- Misses at all speeds - worse @ lower rpm yet will get to 4000rpm. what can be problem- changed plugs, cap, rotor. Starts fine -idles fine.

 

[alldodge]

1999 merc 3.0 chev 4 cyl. with solid state factory ignition- Misses at all speeds - worse @ lower rpm yet will get to 4000rpm. what can be problem- changed plugs, cap, rotor. Starts fine -idles fine.

Sure your not running lean?

 

[dannys2004glastron175mx]

plug wires

 

[achris]

Brand and type of spark plugs?

Should be AC MR43LTS or NGK BPR6EFS. If you have champions, toss them... That's what your problem will be.

 

[Fun Times]

How did the old plugs look? fuel fouled or?

You may need to perform an engine compression test, engine vacuum test and leak down test once you're sure everything else mentioned above seems to check out good including confirming the ignition timing is advancing up to around 23 degrees BTDC between 2400 - 2800 max RPM.