Re: Mercury 150 Optimax optimum rpm while running.
I hate to pick nits but Optimum RPM ---- cruising ---- high speed are mutually exclusive. Optimum RPM is different for each condition. Optimum RPM can mean maximum recommended RPM which is the top of the manufacturers maximum recommended WOT rpm. If the engine can't reach that rpm something is wrong and it is usually the prop or a tune up is needed. Optimum cruising RPM is impossible to specify because there are too many variables. Boat weight, load, water conditions, wind, all affect this. If you are looking for optimum (as in best fuel economy) then the only way to determine that is to install a fuel flow meter. High speed relates to wide open throttle rpm. Again, if the engine can't get there something is wrong. For definition purposes, Cruising is part throttle operation. High speed is wide open throttle.
