Powerful diesels operating at low speed

[Rwnorton]

Help me understand: Ranger , and others, advertise their yachts fuel economy when operating at full displacement speeds and yet they power the yachts to achieve planing/cruising speeds in the teens. What is the long term effect on one of these diesels if the yacht is ONLY operated at the full displacement speed?

If it's called a "tug" why does it have to plane? Does anyone make small tugs that don't plane and have smaller, more economical engines?

 

[Scuffy]

I'm sure others will chime in here. Our boat a R-27 with a 200 hp Volvo D3 gets three to four mpg at 7 or 8 mph. At 5 or 6 mph it's even better. For us we liked the idea of being able to cruise along at 7 or 8 mph. If you need to get somewhere you can run at 16 mph still getting 2.1 mpg. Speeds in between 8 and 14 usually are showing about 1.9 as the boat not as far out the water sort of plowing at those speeds. Our boat topped out at 20 mph but we don't run it that hard. Most folks will run the engine well up on the boost scale and temperature wise (200 degrees or so) every four hours or so just to keep the variable vanned turbo charger exercised and to blow out any carbon build up. The boat weighs about 9000 pounds. Running inlets and other situations requiring a burst of speed now and then I find the boat to be responsive. They are the best of both worlds in my humble opinion. Nice to have the option. I have seen sailboats have to turn around in an inlet because they did not have enough power to exit the inlet. I don't want to be in any boat that's that under powered.

 

[JamesTXSD]

I'm sure you can find older tug-type trawlers that won't move at much more than displacement speed. Or, go with a custom build. People want options (ability to cruise economically AND get up and go when you want or need to), and builders make what people want.

Ranger knows their market. They are responsive to that market. Most people want the option to run at the speed that suits them best.

We have owned sailboats. I know the feeling of wanting "just a few more knots". Think something called a "tug" can't or shouldn't go fast? Google: tug boat races. 😉