How Many Hours on My Engine?

[Dave R]

Originally Posted by secondcurve

Dave:

Thanks. I've been running my motor around 3800-4000 RPMs. I'll slow down a bit. I'm sure this advice will be as good as the advice you gave me on the chart plotter. It works great by the way.

My 3200 RPM rule was specific to the 7.4 MPI Mercruiser in my boat and is mostly due to the long stroke of the engine and utterly stock, GM-sourced, reciprocating mass. My redline is only 4600 RPM. Mercruiser also sold a different 7.4 liter engine, (the 454 MAG) that could be run at (or under) 3600 RPM for excellent longevity. It had a 5000 RPM redline, if memory serves. Merc beefed up much of the reciprocating mass in that engine to handle higher piston speeds. My point is that different engines are going to have different cruising RPM recommendations and 3200 RPM is not necessarily for all engines.

If memory serves, you have an outboard powered rig. 4000 RPM may be a perfectly acceptable (perhaps even low) operating RPM for you.

Glad to hear the chart plotter and Bizer C-map chart are working out well. I love having them aboard my own boat.