best cruising speed

[derock83]

Hey guys, just curious about the best all around rate of travel that you would suggest for my boat. its a 15' 72 tri hull with an 85 hp evinrude from the same year. im looking to cover distance, say maybe a 8-10 mile round trip... but dont want to be too hard on the motor for what its worth. is it possible to go too hard on these old v4 2 strokes? what do you suggest?

 

[KIGuy52]

Re: best cruising speed

My old motor has a "sweet spot" at about 2/3 throttle where it smooths out and sounds just perfect. The speed is fine, so I usually run it right there. I rarely "open it up".

 

[craze1cars]

Re: best cruising speed

Every boat is different, the most accurate way to figure this out is with a fuel flow meter. But that's probably way too expensive for your intended use. Generally just add a few MPH beyond your planing speed. For example, my boat planes out at about 17 to 19 mph, depending on load. So I spend a lot of time cruising at about 22. It feels very efficient at that speed.

 

[magster65]

Re: best cruising speed

I've found (by reading all the numbers and by experience) that around 65% to 70% (a little higher for 2 strokes) of your engine's maximimum rpm there is a 'sweet spot'. This usually works out to the boat's best 'on plane' fuel economy. Hull design has an influence on this too.

 

[SCO]

Re: best cruising speed

The Yamaha engine site has a bunch of performance tests on line. Looking at them, seems most boats get the best MPG's at 3500 to 4000 rpm. I recall 3700 to 4200rpm being the best range for my 18 foot tri w '75 johnson 135hp v4. To get your fuel rate, fill the tank to some known line, run out half the tank at some gps measured test speed, measure the elapsed time, stop engine, and then use a measuring cup to refill the tank to the line. Repeat at different speeds. You'd have info to figure gallons per hour, and miles per gallon( odometer feature on gps would be good way to measure your distance, or calc distance from speed and time)

 

[Solittle]

Re: best cruising speed

If your motor is in good tune and proped right you can run it wide open all day long without hurting it. Might burn a bunch of fuel though.

 

[Ron G]

Re: best cruising speed

I use to have just about the same boat and motor,wot burns alot fuel and fast,mine ran good a liitle over 1/2 throtle.

 

[pine island fred]

Re: best cruising speed

Each time you take the boat out things will have changed a small amout. load,wind tide/current. Each time get in touch with the boat, its a spiritual thing, tweek the trim and throttle till it is ON THE CAM. At this time if you look just right you will see the motor smiling. Then you got it right. Have yet to see a motor that enjoys full power continously, jet,recip,elect Enjoy the rest of the season FRED