You have to define optimum.
Best fuel economy
Top end rpms

Best fuel economy is normally around 3000 to 3500 rpms depending on your
boat and setup.

Top end rpms - not sure on that one but should be around 5000 rpms. Someone
else will have to answer for sure.

--
Tony
my boats at http://t.thomas.home.mchsi.com

"Sylvain Gagnon" wrote in message
.. .
Hi everyone. Looks like this will be the sixth ON TOPIC threads in a row
grin. I have a 1992 Mariner 75 HP two stroke engines. Anybody knows what
would be the optimum RPM for that engine? Thanks.