The factory sticker on my engine (Mercruiser 7.4 MPI, big block GM generation VI) says the WOT RPM should be 4000 - 4400.
With my new propeller I have no problems reaching 4200 RPM when loaded, and 4400 when somewhat empty.
So I am probably OK in terms of propeller pitch vs outdrive gear ratio.
My question is, why my WOT RPM are specified lower than for other similar engines?
I have seen several 7.4 engines with 4200 - 4600 spec, and higher.
Why my engine is considered safe to work under full load at a lower RPM?
Is there a downside to it, like lower compression ratio or worse fuel economy?
Just curious.
With my new propeller I have no problems reaching 4200 RPM when loaded, and 4400 when somewhat empty.
So I am probably OK in terms of propeller pitch vs outdrive gear ratio.
My question is, why my WOT RPM are specified lower than for other similar engines?
I have seen several 7.4 engines with 4200 - 4600 spec, and higher.
Why my engine is considered safe to work under full load at a lower RPM?
Is there a downside to it, like lower compression ratio or worse fuel economy?
Just curious.
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