I tried searching but couldn't find the answer. What is the top end RPM that I shouldn't exceed? also at what RPM are these engines most efficient while running? thanks
Max is 5500 RPM per OEM specs. Most efficient RPM is dependent on what type of boat you have, hull shape, length, weight and propeller pitch etc.
Generally I find that around 4000 RPM's for cruising is a good compromise for fuel consumption vs speed for my set up with a 17 pitch prop. That's somewhere around 30 - 35 MPH on my boat. When I use a 19 pitch prop, the RPM's drop down by 200 - 300 RPM's to achieve the 30 - to 35 MPH, but it seems to use a little more gas.
