"Best cruise speed/rpm"?

[bruceb58]

Can I safely assume that these flow meters work even on carb engines?

Of course. Mine is an a carbed engine.

 

[dingbat]

Best MPG will be at idle speed. Best cruise is the most efficient speed once on plane. Its usually a couple miles an hour above minimum planing speed. The differences in efficiency at the speeds slightly above planing speed are small enough not to really worry about.

Guess your talking about a 4 stroke because the mileage of a 2 stroke at idle is absolutely horrible.

 

[thumpar]

A lot will depend on the engine and boat. My 5.7l EFI likes to cruise at about 3200-3400 RPM.

 

[bruceb58]

Unless you use a flow meter and calculate the MPG, it is basically impossible to determine the most efficient speed by feel.

 

[drrpm]

Did you verify this with a fuel flow meter?
Not personally, but its apparent from every boat test I've seen published.

The reference was for 4-stroke engines. I personally don't think too much about 2 strokes outside of my chainsaw and leaf blower.

 

[keith2k455]

My best cruising speed is measured my the smile on my face. Fuel consumption is not really a factor but I do not have a cruiser boat

Yep, if my kids are on the bow, best cruise speed is 22mph because they want less wind. If everyone is on the back best cruise speed is 35 to 45 mph because my smile meter is in the happy range.

 

[JimS123]

I run a performance check every year. The main reason is to see if there was a change, so I know if I need to rebuild the carb, get new plugs, etc.

The test consists of charting the boat speed at 500 rpm increments and then plotting a graph. I started this before i ever had a PC, so my data is in my log book and was never digitized.

At any rate, gut feeling is good, but the graph confirms the gut. The sweet spot is right at the inflection point on the graph. My published data from the Manufacturer confirms by findings.