MerCruiser Engine Runs Poorly at High RPM 2001-2006

The following information contains troubleshooting testing procedures for engine runs poorly at high rpm problems on the MerCruiser 5.oL, 5.7L and 6.2L MPI gasoline 2001 2002 2003 2004 2005 2006 engines. Testing and diagnosis helps determine problems and possible causes. Its recommended you use a factory manual when performing repairs on your inboard engine, additional safety precautions, or technical data maybe included. 

SYMPTOMS: Engine runs poorly at high rpm

CAUSES

1.0 Crankcase overfilled with oil

1.1 Anti-siphon valve restricting fuel supply

1.2 Plugged fuel tank vent 

1.3 Improper fuel supply

1.4 Incorrect rotor location

1.5 Low grade of fuel or water in the fuel

1.6 Spark plugs fouled, burned, cracked porcelain or incorrect heat range

1.7 Spark plug wires broken or poorly insulated

1.8 Distributor cap or rotor dirty or cracked

1.9 Coil damaged or malfunctioning

1.10 Excessive play in distributor shaft

1.11 Engine overheating

1.12 Low compression - worn valves, rings or seals

1.13 Restricted exhaust 

ACTIONS NEEDED

1.0 Check the oil level with the boat at rest in the water. Drain the oil if necessary to obtain the correct level.

1.1 Check fuel flow rates and repair, replace or remove anti-siphon valve as necessary.

1.2 Clean the fuel tank vent. 

1.3 Inspect fuel supply system. Repair or replace as necessary. 

1.4 Reset rotor location.

1.5 Drain the fuel tank and refill with the correct fuel.

1.6 Inspect the spark plugs and service or replace.

1.7 Replace the spark plug wires.

1.8 Inspect the distributor cap for cracks or marks. Replace the distributor cap and the rotor if necessary.

1.9 Replace the coil. 

1.10 Replace distributor.

1.11 Check cooling water supply or coolant level.

1.12 Perform the cylinder compression check to determine which cylinder has low compression. Replace the rings, the valves or the pistons.

1.13 Clean the exhaust system.

MerCruiser RPM Information

• mercruiser lifter noise high 3500 rpm
• 1995 3l mercruiser engine runs rough at 3000 rpm
• 1999 mercruiser 4.3 high rpm after changing belt and pulley
• 2001 mercruiser 5.0 litre runs hot at 4000 rpms
• 2003 mercruiser 5.7 bravo 2 overheating at high rpms or under load
• 2005 mercruiser 4.3 not reaching wot rpm
• 2005 mercruiser 5.7 mpi wont turn rpms
• 3.0 4 cyl mercruiser overheating at high rpm/hot water going out intake
• 3.0 liter mercruiser running rough at high rpm
• 3.0 mercruiser high rpm wide open and over heat
• 350 magnum fuel cooler engine running hot at 4500 rpm
• 350 magnum mercruiser overheats only at low rpms
• 350 mercruiser boat overheating at high rpms
• 350 mercruiser rough running at 3600 rpm
• 5.7 mercruiser engine miss at hi rpm
• 5.7 mercruiser overheats above 2000 rpms

These service procedures apply to: 2001 2002 2003 2004 2005 2006 Mercury MerCruiser 5.0L, 5.7L, 6.2L MPI Multiport Injection Engine. 5.0L MPI Alpha and Bravo, 350 Alpha and Bravo, 350 MAG MPI Horizon, MX 6.2 MPI, MX 6.2 MPI Horizon, Tow Sports (MIE), 350 MAG MPI, 350 MAG MPI Horizon Inboard, MX 6.2 MPI Inboard, MX 6.2 MPI Horizon Inboard and 350 MAG MPI Tow Sports.