Why does my Mercury MerCruiser MCM 7.4L MPI fluctuate rapidly at idle and then steadies as rpm is increased?
If your Mercury Engine reading fluctuates rapidly at idle but steadies as the rpm increases, the valve guides may be worn.
What causes the Mercury Engine to fluctuate between high and low at idle rpm?
If your Mercury Engine fluctuates between high and low at idle rpm, it could be caused by a blown head gasket between two adjacent cylinders.
What to do if Mercury MerCruiser MCM 7.4L MPI Engine fluctuates 4 or 5 inches very slowly at idle rpm?
If the reading on your Mercury Engine fluctuates 4 or 5 inches very slowly at idle rpm, check if the spark plug gap is too narrow or if the valves are sticking.
General| Engine Type | V8 |
|---|---|
| Bore | 4.25 in (108 mm) |
| Compression Ratio | 8.6:1 |
| Ignition System | Electronic Ignition |
| Alternator | 65 Amp |
| Displacement | 7.4L (454 cu in) |
| Fuel System | Multi-Port Fuel Injection (MPI) |
| Horsepower | 310 HP |
| Torque | 450 lb-ft |
| Cooling System | Closed Cooling |
| Fuel Requirement | 87 octane (minimum) |
| Stroke | 4.00 in (101.6 mm) |
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