mpg

[cmcbob]

does any body have a idea of what mpg a 24 ' sea ray with a new 305 engine will get at a slooooow speed . we are planning a trip 500+ miles .some said 1mpg but we turnd down a 50'nautaline with 2-454 engines because he said it only got 1mpg. #s just dont sound right .
if any body has made the trip from tn to gulf sure would like to here from you bob and betty

 

[paultjohnson]

Re: mpg

It might be worth your time to remove your fuel supply line that goes into your fuel pump , Then run a temp fuel supply from a measured, say 6 gal container, with a measured 6 gal of fuel. Run a temporary fuel line from gas can to fuel pump inlet. Go run it a measured [by gps] 5 miles. at whatever speed you wanna cruise. refill the gas can and see how much you used. Then for shts and giggls go for aW O T run check again,, Then you will always know how much fuel that boat will use at whatever speed . no guessin' hmmm Re reading your post, cant tell if you own that boat yet .. Just an idea
I can never get an acurate fill in my tank, When it sterts gettn full it starts spittn out the vent. I could never tell on my boat exactly how much fuel was in it.. If I wanted to know for sure, I would have to do it this way.To be at all acurate.

 

[kenmyfam]

Re: mpg

No way of assessing MPG due to the load you have, the conditions you are in and the currents you encounter. The only real guideline is GPH (gallons per hour)

 

[rodbolt]

Re: mpg

and there are some really nice books,maps and information on cruising the inland waterways.
it also lists FUEL docks, repair stations and resupply facilities.
PLAN ahead, know about where you will be and what facilities are avalible, take your phone.
make sure your VHF works and what channel the local marinas monitor.
most marinas that handle transients list what channels are monitored.
16 is the hailing and emergency channel, you can always contact the USCG on it and ask them. they will usually have you shift to a working channel, in my area its typically 22 or 22a.

 

[cmcbob]

Re: mpg

thanks for info ,i'll use all of it ,yep shes all mine ,and like any new toy, theres not a spot the size of a dime that i have not sanded, cleaned, shampooed,polished, first boat with teak wood .thanks again

 

[sasto]

Re: mpg

Taking the Tenn-Tom? Down hill all the way.....have fun!

 

[Bob's Garage]

Re: mpg

You might want to look into a Flo-scan system, or some other fuel measuring system. They will give you the information you want on a continuous basis.

Once you get it calibrated it should take out the guess work and make your trip more enjoyable.

 

[45Auto]

Re: mpg

No way of assessing MPG due to the load you have, the conditions you are in and the currents you encounter. The only real guideline is GPH (gallons per hour)

Gallons per hour is irrelevent without speed.

Which of the following is the best cruising speed for a 24' Searay with a 5.0L, and what is it's range? Which one has the best chance of getting me to the next fuel dock 130 miles away?

7.3 GPH at 2500 RPM
8.4 GPH at 3000 RPM
11.3 GPH at 3500 RPM
13.6 GPH at 4000 RPM

No way to tell just from GPH.

 

[45Auto]

Re: mpg

The answer to the post above is the Searay 240's best cruise speed is 23.3 MPH at 3000 RPM. It should be obvious if you look at the MPG column in the chart below which is for a 5.0L fuel injected 24' Searay. In reality, anywhere between about 23 and 35 MPH will give you almost identical fuel economy. Notice how GPH is irrelevent to this and hasn't even been mentioned? You could leave the GPH column out of the chart and it wouldn't make any difference to the discussion.

If you don't understand the relationship between fuel consumption and speed, the chart below will be pretty much meaningless to you.

To the original poster, I would figure on somewhere around 2 MPG depending on the age and load of your boat.

 

[kenmyfam]

Re: mpg

The answer to the post above is the Searay 240's best cruise speed is 23.3 MPH at 3000 RPM. It should be obvious if you look at the MPG column in the chart below which is for a 5.0L fuel injected 24' Searay. In reality, anywhere between about 23 and 35 MPH will give you almost identical fuel economy. Notice how GPH is irrelevent to this and hasn't even been mentioned? You could leave the GPH column out of the chart and it wouldn't make any difference to the discussion.

If you don't understand the relationship between fuel consumption and speed, the chart below will be pretty much meaningless to you.

To the original poster, I would figure on somewhere around 2 MPG depending on the age and load of your boat.

And the MPG with a full tank, a lot of gear, more people and against a strong current in heavier seas would be ????
Your assessment or should I say the boat testers assessment was in calm seas with no wind and did not give any variation for differing conditions.
Guideline for me would include the GPH column and the RPM. Anything else is a huge variable.
Does your tow vehicle get the same MPG going uphill as it does going downhill ??? Do you get the same MPG towing your boat as you do solo ??? then there is the variable of going uphill towing your boat uphill ??? the sea conditions, and loading will give the same variables.
Just my thoughts though.

 

[QC]

Re: mpg

They are good thoughts ken, but I am with 45 that GPH must include speed to be valuable. I believe the variables is why a boat that is tested at 2.7 MPG should be considered as 2 MPG to be conservative.

 

[kenmyfam]

Re: mpg

They are good thoughts ken, but I am with 45 that GPH must include speed to be valuable. I believe the variables is why a boat that is tested at 2.7 MPG should be considered as 2 MPG to be conservative.

Agree. My point was that GPH is an important part of it for "real" calculation of expected fuel consumption. Not irrelevant as stated.

 

[45Auto]

Re: mpg

Does your tow vehicle get the same MPG going uphill as it does going downhill ??? Do you get the same MPG towing your boat as you do solo ??? then there is the variable of going uphill towing your boat uphill ??? the sea conditions, and loading will give the same variables.

Interesting thoughts. So why are you discussing the MPG of a tow vehicle instead of GPH? Do you really bother to figure GPH for your truck? Uphill, downhill, headwind, tailwind, upstream, downstream, high altitude, low altitude, etc, etc, etc. All variables. Doesn't matter if it's a car, boat or truck.

Guideline for me would include the GPH column and the RPM. Anything else is a huge variable.

You really believe that your boat delivers the same GPH at a specific RPM regardless of the load? You obviously have no idea of how a gasoline engine works. The GPH at RPM is a variable which is dependent on the load on the motor.

Put your boat in neutral and rev it up to 3,500 RPM. Notice how it takes very little throttle and very little fuel (low GPH). That's because there is almost no load on the engine. Now get your boat fully loaded with people, fuel, gear, etc. At 3,500 RPM your fuel flow will be about 10 times greater than it was in neutral. Exact same RPM as in neutral, but 10 times the GPH. That's because fuel flow is LOAD DEPENDENT. It is a variable. That's why if you also know your speed, you can cleverly figure your MPG and find your optimum cruise speed.

 

[kenmyfam]

Re: mpg

Interesting thoughts. So why are you discussing the MPG of a tow vehicle instead of GPH? Do you really bother to figure GPH for your truck? Uphill, downhill, headwind, tailwind, upstream, downstream, etc, etc, etc. All variables. Doesn't matter if it's a car, boat or truck.

The gas stations are usually a lot closer on the highway than the open water.

 

[45Auto]

Re: mpg

The gas stations are usually a lot closer on the highway than the open water.

LMAO!!!! This has exactly what to do with the discussion?

If you have a 10 gallons of gas in your boat and it's burning 20 GPH, are you going to make it to a gas dock 15 miles away?

 

[kenmyfam]

Re: mpg

Back to square 1. That's why all aspects should be a part of the calculation.

 

[45Auto]

Re: mpg

Now how did I know he wasn't going to be able to reply to my question?

 

[45Auto]

Re: mpg

Let me re-phrase the question, maybe you can figure it out this time!

If you have 10 gallons of gas in your boat and it's getting 2 miles per gallon, will you be able to make it to a gas dock 15 miles away?

Notice how you can easily answer the question (at least I hope you can!)without knowing speed or GPH? That's because distance, time, and fuel flow are all INCLUDED in the units of MPG.

 

[stylesabu]

Re: mpg

is it windy or calm? if windy, is it at my back? does the boat go over 30 mph?

 

[45Auto]

Re: mpg

is it windy or calm? if windy, is it at my back? does the boat go over 30 mph?

Sorry, according to Kenmyfam you don't need to know the speed, all you need is GPH ......