During sea trial yesterday the engines would not come close to rated RPM of 2350 at WOT. Engine surveyor says there should only be a ~200 - 250 RPM drop when comparing WOT with no load (neutral) and when WOT underway. It may be that the reasons include over-squared economy prop, some slight bottom drag (really not too much growth, maybe 7 out of 10 on the clean side), and slightly bent props (on leading edge). Vessel info is:
1977 Hatt 58 MY (galley up), extensive refit in 2013
DD 8V71TI’s (port engine 1000 hours SMOH / stbd engine 45 hours SMOH)
28x32 wheels
Direct from ER tach readings:
WOT underway
Port: 1855 Stbd: 1892
WOT No load (in neutral)
Port: 2510 Stbd: 2480
So there is a 600+ RPM “droop” instead of the supposed target 200-250 RPM difference.
The engines performed flawlessly in all other respects from start-up to shut-down and all phases of sea trial. Oil analysis (for what it is worth) came back on the low end of the ranges for wear metals and was overall a very good report.
I would greatly appreciate any perspective on what others may have observed or insight in general as whether or not this is something to be concerned about or not. My accept / reject date is October 1.
Many thanks in advance…
Jerry
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RPM question: Engine Survey - Sea trial