1997 Mercruiser 4.3 LX not running steady steady at idle or higher RPM's

[tedwards516]

Hi, I have a 1997 Mercruiser 4.3 LX Gen+ starts fine, but when at idle or at higher RPMs the engine does not run consistently smooth and the RPMs will waiver. Seems like I tried everything but still having the same problem.

• Checked gas for water
• Replaced fuel filter
• Disconnected from main tank and ran off a portable tank
• Compression tested the cylinders
• New Coil, rotor and distributor cap
• New fuel pump
• Cleaned and rebuilt the carb

Probably starts better than ever, but haven't fixed my issues. Any other suggestions? I would also add that the tachometer seems to read higher that what I get on a test tachometer.

 

[Scott06]

Hi, I have a 1997 Mercruiser 4.3 LX Gen+ starts fine, but when at idle or at higher RPMs the engine does not run consistently smooth and the RPMs will waiver. Seems like I tried everything but still having the same problem.

• Checked gas for water
• Replaced fuel filter
• Disconnected from main tank and ran off a portable tank
• Compression tested the cylinders
• New Coil, rotor and distributor cap
• New fuel pump
• Cleaned and rebuilt the carb

Probably starts better than ever, but haven't fixed my issues. Any other suggestions? I would also add that the tachometer seems to read higher that what I get on a test tachometer.

have you set the timing on it and is the timing jumping around. Also disconnect the tach to see if it changes things. Bad tachs can mess with the spark

 

[nola mike]

also doesn't sound like you actually checked the spark