Getting Daydream on a Plane on the Loop

journey on · Posted: Mon Jun 26, 2017 7:40 pm Post subject:

OK, just one more post. It was 102 F outside today so I have a lot of free time.

Pat, I appreciate how heavily loaded you are. I know that the 25 really can be loaded and then goes slow. Judy has learned how to pack Journey On full for our trips and the gas mileage is abysmal.

And if the weight isn't forward, it needs trim tabs.

Boris

thataway · Posted: Mon Jun 26, 2017 9:55 pm Post subject:

Pat,
Thanks for the numbers. You appeared to be getting 2.5 mpg at the 9.5 mph speed, and 1.6 mpg at the 15 mph. (That 1.6 was like I was getting with a 28 footer and 300 hp)... At the 15 mph you appear to be using about 126 HP, at the 9.5 mph you appear to be using about 53 hp. I was questioning if you were really planing at 9.5 mph, especially with heavy load. Always hard to tell at low speeds. Usually when you "get over the bow wave", the fuel consumption decreases. Only if you did that at the 9.5 point, instead of still being on a ascending curve of fuel consumption. No matter, if that is best speed for your "fast" go for it".

in a "light' C dory the planing speed is about 15 mph, and the worse displacement speed is about 10 mph. I realize that there are lots of variables, and comparing the figures on a very light boat are difficult. It would be interesting to compare speeds from 1000 to WOT speeds. Bottom line is that you are now getting to speeds where you are not lugging the motor!

JamesTXSD · Posted: Tue Jun 27, 2017 8:13 am Post subject:

Our experience was different: the most inefficient speeds for our 25 were between 9 and 12 knots. As heavy as you are, I am surprised it could stay on plane at 9 mph. The boat is having to work hard to get over its own bow wave at that speed.

Our experience with the Navman: the read out is not instantaneous. It would read high when the throttle was pushed forward, then (given some time) would settle down. Trim to get the most efficient fuel burn at a given speed/RPM.

And, sometimes to get somewhere, you just use whatever fuel is necessary to get the job done (as long as you have plenty of reserve).

smckean (Tosca) · Posted: Fri Jun 30, 2017 7:53 pm Post subject:

Pat,

I'm sure you're ahead of me on this, but I used to look at GPH when judging fuel burn rates.....nothing wrong with that. But I noticed that I was lazy about converting the readings into what really counts when going from point A to point B; namely, MPG. At the higher RPMs, one surely uses more fuel per hour (except just after the planing transition), but one also goes more miles per hour.

Here are numbers I got in 2015 on the Honda 150 before it blew up. Of course, I was not heavily loaded like you are. Last year we took a 8 day cruise to Canada and were loaded heavy (not as heavy as you, no doubt), and I was amazed how sluggish that made everything.

RPM; MPH; GPH; MPG
3000; 9.7; 4.5; 2.2
3500 13.0; 4.6; 2.8 (just planing)
4000 17.9; 6.5; 2.8
4500 23.0; 7.7; 3.0