at 3800 rpm's, I burn 14.5 gallons per hour according to my smarcraft gauge.

 

Do you find that you come up with the same number ALL the time? I wonder if a boat doesn't always require the same "effort" to aquire a certain RPM. Depending on the load in the boat, fuel, wind, waves, tide.....

I guess what I am saying is the throttle position may not always be the same at a given RPM. I guess I can check that too. This software also shows the throttle position.

 

Do you find that you come up with the same number ALL the time? I wonder if a boat doesn't always require the same "effort" to aquire a certain RPM. Depending on the load in the boat, fuel, wind, waves, tide.....

I guess what I am saying is the throttle position may not always be the same at a given RPM. I guess I can check that too. This software also shows the throttle position.

It is always within .10ths everytime. I always start the day full of fuel amd most of the time it is 2 of us. Consumption also stays the same weather I am going against or with the current, only thing that changes is speed. But, I run by RPM, not speed.

These numbers are also from when I had my 1 inch spacer. I have run a few times this year without the spacer and fuel consumption went up buy about 1 gallon per hour in the 3200-4000 rpm range. That is all I checked it at. This weekend, i will be running a 1/2 inch spacer and I wil see where I come in at...

 

Great info guys. What about MPG?

 

Ahhh..... who cares? Seriously though. We don't buy BBC's to worry about fuel consumption rates/ mpg's........ I know thats the last thing on my mind when I crank it up.

My boat has 2 speeds..... Idle and WFO.

 

Ahhh..... who cares? Seriously though. We don't buy BBC's to worry about fuel consumption rates/ mpg's........ I know thats the last thing on my mind when I crank it up.

My boat has 2 speeds..... Idle and WFO.

I don't dwell on these figures all day or anything. The reason I do care is so I'm not floating in the middle of the Chesapeake Bay after running out of gas.

Actually, more important than these figures is my average GPH. I arrive at that by dividing the gallons used by the run hours since the last fill. I come up with about 10-12 GPH pretty consistantly. This is a mix of idel, cruise, and wot. Being that boat gas guages are what they are, I know I can run approx. 5 hours on a tanks of gas.

 

Neet info, I wonder how the 496HO compares to the hp500efi?

Hey Super24, go out and get a set of CMI headers and check the fuel consumption after. CMI claims better fuel economy. That software is a great platform for testing.

 

Neet info, I wonder how the 496HO compares to the hp500efi?

Hey Super24, go out and get a set of CMI headers and check the fuel consumption after. CMI claims better fuel economy. That software is a great platform for testing.

I think it can read some basic info from the 500efi but it doesn't have all the sensors that the 496s and 5252s have. I know this software can communicate with the 525efi.

CMI's.....that would be an expensive test....you first! :laugher:

 

I already have em

 

4100 to 4500 makes a good leap..

 

To find your boats 'sweet 'spot you really need to look at the MPG at each RPM. On your next run record the MPH at each of your RPMs and then divide the MPH by GPH and this will give you the MPG. I would bet that the best will be around 3000 RPM. You can then multiply the MPG times the total fuel capicity of your boat and see the max. range your boat will go at each rpm and MPH.
For example if at 3000 you are running 35MPH and using 11.67GPH = 3MPG and 60gal fuel = 180 miles and then at 4600 rpm you are doing 60MPH and using 30.1GPH = 2MPG and 60 gal fuel = 120 miles.

 

How much does the software cost?

I would think around 4K would be an efficient cruise speed for most boats wouldnt it?

 

Most boats tested in the mags have best mpg between 3000-3500 rpm.

 

Most boats tested in the mags have best mpg between 3000-3500 rpm.

That seems to be true from the facts I've gathered. My boat gets slightly better economy at 3K than 3500, but the boat doesn't feel as good. My prop seems to slip a lot between 28-3200.

Cobra Marty, I see what you are saying. Assuming I left the marina and cruised continuously that method would be most accurate. Although I can tell by looking at the total engine hours in my report, approx. 25% of the hours are at idle. So, for the purpose of not running out of gas, my average GPH method seems to work well.

Not right, The SW was around $450, but you need a laptop too. The merc scan tool was slightly cheaper but not as cool as Diacom.

OK, here's my conclusion to all this.....

This is the sweet spot as far as I can tell.
3400 RPMs = 15 GPH
60 Gallon tank = 4 hours
4 x 56mph@3400rpm = 224 miles
224 / 60 = 3.7 MPG

 

How do you hooh it to the boat? Just to the ECM? The program comes with the adapters I assume?

Thats really good milage at 3400!

 

How do you hooh it to the boat? Just to the ECM? The program comes with the adapters I assume?

Thats really good milage at 3400!

It comes with everthing you need. It has two different cable ends, one fits my 496, I think the other one is for the older style motors. The other end is USB that plugs into your laptop. The 496 has a little pigtail that you plug into. I hook everything up, hit "record" then ride as long as I want and it records everything. Then you save the file and you can view it anytime you want, in graph or text format.

 

Sweet Spot. In the summer heat, with a moderate load, 4000 rpm seems the sweet spot for my boat. At 3500-oil temps were 215-dropped to 190 at 4000. same water pressure so I assumed the engine was working harder or behind the curve at 3500. Going by feel and sound-4000 was it. Stuchamp called it harmonics. Important to learn to feel and hear you engine.

 

Sweet Spot. In the summer heat, with a moderate load, 4000 rpm seems the sweet spot for my boat. At 3500-oil temps were 215-dropped to 190 at 4000. same water pressure so I assumed the engine was working harder or behind the curve at 3500. Going by feel and sound-4000 was it. Stuchamp called it harmonics. Important to learn to feel and hear you engine.

Do you have Smartcraft or an oil temp gauge? Oil temp seems to be one of the few things this SW does not tell you.

 

for $450 you can get a navman depthometer and two fuel flow meters - put them in line and plug the wires into the depthometer and you have fuel consumed, gph,mpg in real time.

 

Gauges

 

for $450 you can get a navman depthometer and two fuel flow meters - put them in line and plug the wires into the depthometer and you have fuel consumed, gph,mpg in real time.

Perhaps, but GPH is only a fraction of what this SW tells you. Most importantly, trouble codes. Plus, more things that I feel like typing here. It's a diagnostic tool, I didn't buy it for the sole purpose of finding out my fuel consumtion.

 

Gauges

That's what I figured. Does the 496HO have an oil temp sensor? Or, did you add one?

 

I come up with about 10-12 GPH pretty consistantly. This is a mix of idel, cruise, and wot.

I must spend way too much time in no wake zones. My average over the last four seasons is right around 12 gph. (I know because I keep all my gas receipts for fuel tax refund.) That is for twin HO's. :

 

For the owners of 496HO's. Ever wonder how much fuel your motor burns? Now that gas is so expensive, I'm trying to find that "sweet" spot. Using Diacom software this was my findings from today.

RPM GPH
700 1.61
750 2.0
850 2.17
1070 4.26
1525 5.67
2000 8.55
2100 9.22
2200 9.57
2400 10.43
2800 10.55
3000 11.67
3300 14.5
3500 16.49
3800 19.51
3900 19.73
4000 21.17
4100 22.98
4500 29.26
4600 30.1
4700 32.21
4800 33.32
4900 33.64
4950 34

looks like 3000 rpm is your sweet spot...

 

Re: Re: 496HO fuel consumption

looks like 3000 rpm is your sweet spot...

Going strictly by the math that is true. But, my boat doesn't seem to like riding at 3000. My prop doesn't feel completely hooked up. Also, my bottom has a pad and I don't feel like I am up on the pad like I should be.