best rpm to run an engine

[ibeiser]

The manual for my Suzuki 115HP outboard engine says the operating rpm is 5,000-6,000. My question: is there an "optimum" operating rpm for 1. efficiency? 2. engine longevity (less wear and tear)? Is the engine more likely to overheat or break down if operated constantly at the max rpm and is is better to operate it a lower rpm instead? any other recommendations for best rpm to running an engine?

 

[Silvertip]

Re: best rpm to run an engine

The engine is designed to run anywhere from idle to 6000 rpm. Best fuel ECONOMY is hard to predict since it depends on the boat type, load, etc. Fuel EFFICIENCY is often confused with fuel economy and they are two different measures. Best efficiency is at wide open throttle. Thats where you get the most power on available fuel. That is far different than best fuel economy. There is no requirement to operate the engine at 5000, 6000 or 2000 rpm. It is designed to run continuously at 6000 rpm. It should come as no surprise that just like a car or truck or any other device with an engine -- run it wide open all the time and it will not last as long as it would throttled back. Run where you need to. If you are in a hurry -- run wide open. If not -- 4000 to 4500 should be a nice comfortable cruising speed.

 

[pine island fred]

Re: best rpm to run an engine

Agree with SILVERTIP. After you have operated the motor for awhile, you should be able to MIND MELD with the unit and know when it is happy, ON THE CAM. With my 4 stroke it is around 4000 rpm. Other piston engines that turn props have 4 power setting. Idle, take off, climb and cruise, O/Bs are the same way. An awful lot of people have only 2 power setting, idle no wake and WOT. Their motors but it has to be detrimental to the units.
One exception comes to mind, useless information. The engines on C-130s and P-3s ( electras ) are always turning at 100% and power is controlled by the pitch of the prop. Arnt you happy I told you that? regards FRED

 

[pecheux]

Re: best rpm to run an engine

Like Fred wrote you should be able to tell by the sound of the motor when it's running happy with the least effort (sweet spot rpm) Boat weight, prop pitch, and several other factors, makes a big difference from boat to boat.

 

[ibeiser]

Re: best rpm to run an engine

thanks everyone for the info

 

[Outsider]

Re: best rpm to run an engine

The engines on C-130s and P-3s ( electras ) are always turning at 100%

Yeah, knowledge of turboprops is not really relevant to this discussion ... :facepalm:

 

[robert graham]

Re: best rpm to run an engine

Check: Yamaha Outboard Performance Bulletins for good information regarding GPH, MPG, MPH,etc. for various boat/motor set-ups. My 90HP gets best MPG about 3500RPM's, just on plane. Running WOT gets you a few more MPH, but burns the heck out of the fuel, and at gas prices these days I usually run a bit slower than I used to! Good Luck!

 

[pine island fred]

Re: best rpm to run an engine

I did mention that it was USELESS INFORMATION. Like everything else posted is relevant? FRED