Saving boat gas.

[BroadHopper]

Did a search on this forum and I don't see a thread on how to save gas. So here goes.

Somewhere on my INTERNET search, I read, if you have a boat and get 10 GPH or better (less) you have pretty good boat. I'm wondering what folks are getting around the Lakes Region area. And what steps are taking to conserve gas, beside the obvious 'dock your boat'.

I have been experimenting with different props. My 1988 F223-LS with the 7.4 liter engine and Bravo drive originally came with a 19' SS 3 blade prop. I am the second owner. GPH at the time was 11. Since I was bumping the rev limiter at WOT, I decided to switch to a 23' SS 3 blade. This is the recommended prop for the 7.4 liter by Mercury marine. My GPH with this prop is 9 GPH. With light load and half tank of gas, I was hitting the rev limiter at WOT. I decided to switch to a 25' SS 3 blade. My GPH increased to 7.95 GPH. Since I was experiencing prop blowouts, I decided to switch to a 24' SS 4 blade. Blowouts are gone. I do not hit the rev limiter at light loads situations. My GPH slightly decrease to 8 GPH.

Bear in mind my average RPM is between 2500 and 3000 RPM. I normally leave with a full tank and 3 adults. The GPH readings are the average of several trips for each prop. At 2500 rpm my GPS speed is 30 mph.

By changing props, I save 3 GPH. A 37.5% savings.

Any other ideas to save gas?

[NoBozo]

I burn 3.5/4.0 GPH with a 5.7 (350) V8 in a 20 foot Donzi with a 21" Cleaver prop. . The tank is always kept at half full or better. This includes an occasional Speed Run just to blow the carbon out...but I NEVER NEVER exceed the 45 MPH thingy that we can't talk about. NEVER. NB

[jrc]

Sounds like you dialed in the right prop. As you know, you want a prop that gets you to the reccomended max rpm at WOT, this should be a little below rev limiter. Any more prop and you will overload your engine and risk premature wear. Any less and you risk over-revving, use more fuel but will have a better hole shot (gets on plane faster).

Did you see as much improvement in MPG as in GPH?

My solutions are all pretty obvious:

Spend more time at anchor. I hate staying at the dock in good weather, so even if I just go out a mile and anchor.

Pack a lunch to avoid driving to the other end of the lake for food. I can't tell you how many times I spent more for gas than food.

Find a sweet spot to cruise. I don't have fuel flow meter, but most boats get the best economy at either idle speed or fully on plane. I avoid running in the plowing zone and running at full speed. In general, the smaller the wake the lower the fuel usage.

[Dave R]

Broadhopper, while I am reasonably sure you are indeed using less fuel with the current prop, the only real way to measure fuel economy is through MPG.

I have a Lowrance LMF200 with a paddle wheel speed sensor and a fuel flow probe. It displays MPG (and all kinds of other parameters) in real time. I replaced my gas gauge with it at my helm as it's also an incredibly accurate (within 1%) gas gauge. It will connect to a GPS with NMEA2000 outputs for very accurate speed readings.

I've discovered that my best cruising speed is around 32 MPH, but that I get nearly the same gas mileage between 28 and 40 MPH.

[ishoot308]

Best fuel efficiency in my boat at cruising speed (around 3000 RPM) is about 8.3 gallons per hour. At W.O.T. (AROUND 5800 rpm) that drastically decreases to about 26 gallons per hour, but what fun!!

Saving gas while boating all depends on what you are trying to accomplish.

If you want more hours on the water with less gas being used simply throttle down. If you are looking to economically get from point A to point B you need to find the proper cruising speed for your boat and motor.

Having the right prop can make a world of difference in gas savings at cruising speed. Your motor should be propped so at normal load your required / recommended W.O.T. RPM's are attained. I have tried many props to ensure I am getting everything I can out of my boat and feel it has been well worth the effort.


Dan

[Dave R]

Originally Posted by ishoot308

Best fuel efficiency in my boat at cruising speed (around 3000 RPM) is about 8.3 gallons per hour. At W.O.T. (AROUND 5800 rpm) that drastically decreases to about 26 gallons per hour, but what fun!!

Whatcha got that runs 5800 RPM? Thinking it's a 320-350 HP engine or so, but not an I/O.

[ishoot308]

Originally Posted by Dave R

Whatcha got that runs 5800 RPM? Thinking it's a 320-350 HP engine or so, but not an I/O.

I guess I should have noted that! It's and Evinrude Etec 250 HO outboard.

Dan

[Dave R]

Originally Posted by ishoot308

I guess I should have noted that! It's and Evinrude Etec 250 HO outboard.

Dan

Gotcha. There's a pretty big drop in economy at WOT on two stroke, even a modern one. I imagine if you back down a bit from WOT, the GPH drops quite a bit.

[Lakegeezer]

I get 2 MPG more when coasting downhill.

[BroadHopper]

My daughter gave me a Garmin Nuvi 255 for Christmas. I am trying to get the most out of it. I downloaded the Winni map and installed it. I use it last Tuesday for the first time. I neglected to reset the trip odometer, so I do not have MPG result. Once I set it up, I should be able to calculate the mpg.

I do know that GPS are only accurate in a straight line. It is the only way I can calculate distance.

I notice the VDO speedometer with the pitot tube is fairly accurate around 30 mph. Before and after that it records the wrong speed exponentially as you go slower or faster.

I will let you know what I find out.

[NoBozo]

Originally Posted by BroadHopper

I do know that GPS are only accurate in a straight line. It is the only way I can calculate distance. .

BH: This is not really true. If it were..the GPS would not leave the "Breadcrumbs" track in memory. NB

[ishoot308]

Originally Posted by Dave R

Gotcha. There's a pretty big drop in economy at WOT on two stroke, even a modern one. I imagine if you back down a bit from WOT, the GPH drops quite a bit.

Yes you are correct because At 4000 RPM I get around 12 GPH.

Supposedly it's the most fuel efficient and lowest emission outboard currently produced including the four strokes!

Dan

[SIKSUKR]

I like to draft behind bigger boats.I find if I stay within 10 ft I cut my gph in half.Going through the channel towards Paugus always uses 1/2 the fuel of returning.

[VtSteve]

Originally Posted by Dave R

Broadhopper, while I am reasonably sure you are indeed using less fuel with the current prop, the only real way to measure fuel economy is through MPG.

I have a Lowrance LMF200 with a paddle wheel speed sensor and a fuel flow probe. It displays MPG (and all kinds of other parameters) in real time. I replaced my gas gauge with it at my helm as it's also an incredibly accurate (within 1%) gas gauge. It will connect to a GPS with NMEA2000 outputs for very accurate speed readings.

I've discovered that my best cruising speed is around 32 MPH, but that I get nearly the same gas mileage between 28 and 40 MPH.

I've been thinking of adding something to my Garmin 440, but can't seem to find any info on their site. My unit can be used with a transducer, which would show depth and water temp. But I can never seem to find any info where I can hook it up to the mercruiser engine, which is fully smartcraft enabled as well.

[Sman]

I suppose if the bottom of your boat is not crapped up that could only help, maybe negligible, what about trim tabs...is bow down plowing going to hurt it

I have never checked mine, 350block/260hp/24'deepV. I also don't keep the tank full. Unlike nobozo I am at half full or less most of the time, maybe that helps, not sure, less weight, but doing it that way doesn't help me calculate what I use, no fancy electronics on board.

with my car I am all over that stat, but never checked it with the boat, don't think I wanted to know the answer

[LIforrelaxin]

I solved the whole MPG, GPH debate at my dock.... I decided I just wasn't going to worry about it... I instead worry about FPG (Fun Per Gallon) and FPH (FUN Per Hour) and last FPCU (Fun Per Cost Unit).... As of yet I haven't found the right unit to really measure Fun in... so I have no figures... But the smiles on the faces of My Wife and step Children, tell me.... "for everything else there is Visa".....

End of my story.......

[Dave R]

Originally Posted by VtSteve

I've been thinking of adding something to my Garmin 440, but can't seem to find any info on their site. My unit can be used with a transducer, which would show depth and water temp. But I can never seem to find any info where I can hook it up to the mercruiser engine, which is fully smartcraft enabled as well.

The 440 has an NMEA0183 interface that can connect directly to the smart craft wiring. You'll only need to connect two pairs of wires together, tell the smart craft that it gets speed data from the GPS, enable the NMEA0183 port on the GPS, and then the GPS will share data with smart craft.

[Dave R]

Originally Posted by Sman

I suppose if the bottom of your boat is not crapped up that could only help, maybe negligible, what about trim tabs...is bow down plowing going to hurt it

I have never checked mine, 350block/260hp/24'deepV. I also don't keep the tank full. Unlike nobozo I am at half full or less most of the time, maybe that helps, not sure, less weight, but doing it that way doesn't help me calculate what I use, no fancy electronics on board.

with my car I am all over that stat, but never checked it with the boat, don't think I wanted to know the answer

Trim tabs will hurt MPG. You want to be cleanly up on plane, drive trimmed out for best speed, tabs deployed as little as possible, and engine running 3000 to 3500 RPM for optimal gas mileage (on plane, the boat will get best MPG at idle speed)

[VtSteve]

Dave, it seems there are too many ways to get to various points. I still couldn't find much on the Garmin site, but I did Google this up.

http://my.boatus.com/forum/forum_pos...TID=65159&PN=2

I have regular old fashioned analog gauges. The two things I'd love to have access too are the fuel economy readings, plus the engine RPM. The prices this guy states kind of threw me back.

[NoBozo]

For those who may not know: Here's how you figure how many Gallons Per Hour (GPH) you are using....which is the Only credible way to measure fuel use in a boat. MPG is for Road Vehicles. Cars have NO SLIP passing over the road. Boats have SLIP because propellers are not as efficient as rubber on the road.

The only instrument you need on the boat is an engine "Hour Meter"....and a $6 calculator.

Fill up the tank and NOTE ...(Write It Down) the reading on your hour meter. Drive the boat for however amount of time you feel like risking running out of gas. How Lucky ARE You Feeling today? Go to the marina and gas up...FULL TANK.

NOTE how many gallons you Take On to FILL the tank. Get out your little calculator and determine how many hours you have used the boat since you Last FILLED UP the tank. Say you have used the boat for 10 hours. Now look up at the fuel pump on the dock and see how many gallons you just pumped into the boat. Lets say you pumped 30 Gallons.

So you used 30 gallons....in 10 hours of use. Enter 30 into your calculator and DIVIDE by 10. You will get 3 GPH.

This seems pretty simple and will insult those who already know this but those who don't....... may find it usefull.

So write this formula down... Gallons Pumped to FILL UP.. divided by Hours since the last FILLUP. NB

[Dave R]

Originally Posted by VtSteve

Dave, it seems there are too many ways to get to various points. I still couldn't find much on the Garmin site, but I did Google this up.

http://my.boatus.com/forum/forum_pos...TID=65159&PN=2

I have regular old fashioned analog gauges. The two things I'd love to have access too are the fuel economy readings, plus the engine RPM. The prices this guy states kind of threw me back.

The up-front price is the downside of smart craft. If you go with lowrance, the gauge is cheaper, but all the sensors you need to do everything smart craft does would likely cost more in total, and Lowrance is not compatible with your Garmin so you would not have GPS speed with Lowrance.

[Rattlesnake Gal]

Originally Posted by Lakegeezer

I get 2 MPG more when coasting downhill.

Thanks for the laugh Lakegeezer! Those hills on the lake can either hurt you or help you.

[Wolfeboro_Baja]

Originally Posted by Rattlesnake Gal

Thanks for the laugh Lakegeezer! Those hills on the lake can either hurt you or help you.

But, but............if you're not under power, don't you lose directional control????

[hancoveguy]

Originally Posted by LIforrelaxin

I solved the whole MPG, GPH debate at my dock.... I decided I just wasn't going to worry about it... I instead worry about FPG (Fun Per Gallon) and FPH (FUN Per Hour) and last FPCU (Fun Per Cost Unit).... As of yet I haven't found the right unit to really measure Fun in... so I have no figures... But the smiles on the faces of My Wife and step Children, tell me.... "for everything else there is Visa".....

End of my story.......

I find that the unit of measure (whatever it is) is directly proportional to every hour before 9pm the kids fall asleep.
Example- Many, many fun units = kids asleep on the couch by 830pm as opposed to- Many,many,many,many fun units = kids asleep in boat on the way back to the dock...

HCG

[Rattlesnake Guy]

Originally Posted by Lakegeezer

I get 2 MPG more when coasting downhill.

With the curvature of the earth, we seem to be going up hill all the time.

[Rattlesnake Guy]

I think by previous calculations we found that the smaller your wake, the better the gas mileage. Until you get on plane and then the faster you go the worse the miles per gallon. So best at no wake or just on plane depending on how fast you want to go. We spend most of our boating hours just on plane.

[Irrigation Guy]

I think you need to be just a bit faster than "just on plane". Fast enough that you're not pushing too much water up into a good sized wake(so the stern is not digging in).

[trfour]

Originally Posted by Rattlesnake Guy

I think by previous calculations we found that the smaller your wake, the better the gas mileage. Until you get on plane and then the faster you go the worse the miles per gallon. So best at no wake or just on plane depending on how fast you want to go. We spend most of our boating hours just on plane.

Dear Rattlesnake Guy. Please keep you're [ Miles Per Gallon Recipes In There Proper Place, As In The Glove Box Of The Tow Vehicle ]...
When out in and or about in a Boat, fuel consumption takes on a whole 'nother aspect... I am not here to pick on you!... However, we all have a certain responsibility to guide folks in a direction appropriate to this very beloved Lake.

Wave action can and will exceed shoreline elevations... And this is the why and therefore 'Gallons Per Hour' has always been the rule of thumb in any marine environment.
The waves or up hills out in the broads can and have surprised me, and when you get to coast down the other side of the aforementioned, It is truly a thrill.

All us LakeGeezers rode 'um and surved'um to carry on the Great Spirit here that reaches way back into history.


I'm no Einstein, however I will admit to learning from, and being here to pass on what I have.

Terry
_________________________________________

[robmac]

IMHO,if you have to be overly concerned with GPH perhaps a blow or paddle boat would serve you better. When it comes to boating you know from the beginning it's expensive,I'll find another way to save for it or another way to earn more so we don't go without something we need. It's about enjoying the outdoors and being on the water,with family,friends and those you meet. Just my opinion.

[upthesaukee]

Don't waste time running the blower prior to engine start, because I heard the alternator has to work harder to recharge the battery from running the blower. Start up and get on plane as quickly as possible and don't worry about no wake zones such as Alton or coming out of Merideth. Go in a straight line and don't worry about other boaters...they will get out of your way because you have the right of way. When you get to your destination, jump into the first dock spot you find, and don't worry about other boaters who were waiting. Obviously they have the time to wait, and they will get over it. On your way home, just follow the same type procedures.

Signed

Capt. Bonehead.

Scary thing is some folks probably really think this way.

[jrc]

With due respect to NoBozo, I don't find GPH useful for determining the efficiency of my boating. It's way too dependent on speed. If I take an extra pass through the Weirs channel or Sally's gut my GPH will improve but I really havn't done anything to improve my boat operation.

You really need an fuel flow meter to monitor in real time. Say I want to boat over to Wolfeboro, what is best speed to go there. The very best speed will be around 5 MPH but that's four hours round trip. What's the best on-plane speed? I don't have the equipment, but I can guess it's better at 25 MPH than at 12 MPH. But my GPH will be better at 12 MPH.

[brk-lnt]

Originally Posted by jrc

You really need an fuel flow meter to monitor in real time. Say I want to boat over to Wolfeboro, what is best speed to go there. The very best speed will be around 5 MPH but that's four hours round trip. What's the best on-plane speed? I don't have the equipment, but I can guess it's better at 25 MPH than at 12 MPH. But my GPH will be better at 12 MPH.

You're correct, but then you still have to do the final math...

Let's say at 5MPH you're burning 2GPH. To go 25 miles would take 5 hours. Hours x 2GPH would be 10 Gallons burned to make the trip.

At 25MPH you might be burning 9GPH. To go 25 miles would take 1 hour and you'd burn 9 gallons (making better time and less fuel than the 5MPH ride).

At 12MPH you might burn 6GPH. A 25 mile ride would take a little over 2 hours and 12 gallons.

(These are all just made-up numbers, but hopefully you get the idea).

You have to factor GPH, and time/distance.

[NoBozo]

I had a 32 foot.. 10,500 pound Sailboat over 25 years ago. I sailed it to Bermuda in 1981..but that is irrelevant. It had a 15HP Yanmar diesel. It burned 1/5 GPH. Yup..I'm not making this up....real world experience. That's ONE gallon every FIVE hours....BTW at 6 Knots. I am an engineer and as such am obsessed with keeping records. NB

[brk-lnt]

Originally Posted by NoBozo

I had a 32 foot.. 10,500 pound Sailboat over 25 years ago. I sailed it to Bermuda in 1981..but that is irrelevant. It had a 15HP Yanmar diesel. It burned 1/5 GPH. Yup..I'm not making this up....real world experience. That's ONE gallon every FIVE hours....BTW at 6 Knots. I am an engineer and as such am obsessed with keeping records. NB

Not surprised at all. A diesel engine on a sailboat hull (which by design is generally engineered for minimal drag and high efficiency in the water), I find that totally believable.

[jrc]

brk-int, the fuel flow meter I have my eye on connects to my GPS and does all the math.

NoBozo, that's an impressive number. According to boattest.com, my boat uses about 7 times that at 6 knots.

I'm an engineer as well but I don't have records from that far back. Not that I had a boat in 1981.

[gtxrider]

Originally Posted by Rattlesnake Guy

With the curvature of the earth, we seem to be going up hill all the time.

Up Hill or Down Hill depends on if you are going east to west or west to east. It was differnt in the old days when you walked to school in the snow with no shoes it was up hill both ways.

I have seen some big hills on the lake caused by BIG BOATS not up on a plane!

[VitaBene]

Originally Posted by gtxrider

Up Hill or Down Hill depends on if you are going east to west or west to east. It was differnt in the old days when you walked to school in the snow with no shoes it was up hill both ways.

I have seen some big hills on the lake caused by BIG BOATS not up on a plane!

Aren't those fun for you 'ski riders!!

[White Rook]

Originally Posted by NoBozo

I burn 3.5/4.0 GPH with a 5.7 (350) V8 in a 20 foot Donzi with a 21" Cleaver prop. . The tank is always kept at half full or better. This includes an occasional Speed Run just to blow the carbon out...but I NEVER NEVER exceed the 45 MPH thingy that we can't talk about. NEVER. NB

Here's the "Formula" that I use to monitor fuel consumption on my 1986 F-242-LS with twin 350's. It's actually quite simple. When the fuel gauge needle moves to the far left, I keep spending money to move the gauge needle back to the far right. There see ..... simple math.

[trfour]

Mostly in a five gallon gas can clearly marked [ lawnmower/boat ] stored in the utility shed at the camp, so's any time I got back in from boating late I always had gas enough to make it to Lakeport Landing the next day to refuel.



Terry
________________________________

[NoBozo]

I never let the gas guage go below 1/2. The first year I had the boat I went out after supper for a little ride. I NOTED the gas guage said I had just a hair over 1/2 tank. That would be half of 40 gallons. No Problem. 30 minutes later I was out of gas. Bummer at night.

Boat gas guages are notoriously inacurate for two reasons: Firstly, the gas tanks are iregularly shaped to fit into confined irregular shaped spaces. So if the guage says you have 1/2 tank..that does NOT mean you have half of the tanks total capacity left.

The second reason is that the electro-mechanical float sensor mechanism in the tank takes a terrible beating, bouncing around in there every time you fly over and into a wave.

Experience is a good teacher..it makes you remember. Nb

[Winnipesaukee]

Originally Posted by NoBozo

I burn 3.5/4.0 GPH with a 5.7 (350) V8 in a 20 foot Donzi with a 21" Cleaver prop. . The tank is always kept at half full or better. This includes an occasional Speed Run just to blow the carbon out...but I NEVER NEVER exceed the 45 MPH thingy that we can't talk about. NEVER. NB

That's called an Italian Tune-Up.