General Discussion

Here is my report from my test run today, please tell me exactly what you think is wrong with my starboard engine? Is it obvious?

Starboard Engine Test Run

August 22, 2025

Vessel: 1973 36’ Chris-Craft Commander Sports Cruisers/Tournament Fisherman

Test Conditions

• Date/Time: Friday, August 22, 2025. Departure ~2:15 PM, return ~4:15 PM

• Fuel Load: Full tanks

• Engines: Twin GM 454s (closed cooling, electronic ignition)

• Sea Conditions: Fairly calm/light chop for New York Harbor.

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Starboard Engine Maintenance Completed Prior to Test:

• Compression test - All 8 cylinders equal

• Cooling system pressure test Held pressure, no apparent leaks

• Spark plug wires replaced

• Fuel filters replaced

• Oil and coolant levels checked

• 
  

Performance Data

RPM Average Speed (knots)

3000 11.3

3200 14.0

3600 19.5

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Engine Observations

Engine Temp Oil Pressure Performance Notes

Port

~137°F

80 psi Normal, smooth across RPM range

Starboard

150°F

60–70psi

Falters above 3000 RPM; initially at 3400 RPM, then 3200 RPM, finally at 3000 RPM; runs smoothly at/below 3000 RPM. White smoke observed from exhaust, more than port engine and more than normal boat exhaust, color is white or very light gray, not blue or dark gray.

Conclusions

• Starboard engine falters consistently above ~3000 RPM under load

• Issue progresses with run time; possible heat-related ignition/fuel delivery weakness or water intrusion

• Cooling and oil pressure readings within normal limits

• White smoke suggests possible coolant entering combustion chamber

• Issue repeatable; not resolved by recent wire/filter replacement