Fuel Performance Data vs RPM

[tboltmike]

This doc includes text and chart describing fuel consumption as a function of RPM. Include speed, use rate and MPG.

This for my Arrow Glass Cheetah trihull with the original 115 hp Johnson.

Hope you find it interesting.

Mike

 

[180Fisherman]

Re: Fuel Performance Data vs RPM

Interesting stuff. No way on earth I could run my Johnson 115 at 3250 rpms though. Way too low on my 18' CC. I doubt she'd stay on plane.

 

[Silvertip]

Re: Fuel Performance Data vs RPM

The reason you see such a spread on a paddle wheel vs gps speed is the same reason pitot speedometers don't begin to read with any semblance of accuracy below 10 mph. The fuel consumption numbers may also be skewed negatively since you are lugging the engine. 5100 is way too low at WOT for that engine so a prop change and/or engine height adjustment is needed to bring rpm up.

 

[tboltmike]

Re: Fuel Performance Data vs RPM

Thanks for the responses

I'm finishing up the restore and the prop pitch is in the scope. However, the engine was detuned back in the 80's as per a bulletin from OMC during the switch to unleaded. I've been discussing getting the timing reset to original to see if that adds more RPM.

The manual states that the engine is rated at 115 at 5000, and that WOT range is 4500 to 5500.

It is interesting that the original Airguide speedo above 10 mph is more accurate than the paddle and very close to the gps.