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AaronM

Where are the fuel efficient boats?

45 posts in this topic

I have a '96 Lund 16 foot ProV with a 115 Evinrude Intruder. Because of the high prices of gas last summer, I became really concerned about the fuel consumption of the motor. Running at about 3,500 RPM (Around 30 MPH) I got around 3 MPG. Cruising at 5,200 RPM (45 MPH) brought me less than 3 MPG. I've been thinking of selling the boat to find something more fuel efficient, but the new November Bass Master had a great article featuring rigs and their fuel efficiency that really opened my eyes.

From Yamaha, Mercury and Evinrude (over 115 HP), the AVERAGE MPG at 3,500 RPM was around 4.5. A few motors (Yamaha F115TLR, Mercury Pro XS 250, and the Evinrude E-Tec 175) were above 5 MPG at 3,500. No boats operated at above 5 MPG at WOT.

What gives? I thought because of the age of my motor I was really getting the shaft at the pump, but I guess I'm not that far off. Where are the fuel efficient boats?

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Good topic. I noticed this summer pulling the kids on a tube with a 175 sportfish on a 125 merc 2+2 i averagered about 1.5 to 2 mpg. If my car did that to me It would be in the shop the next day.

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I average about 4 mpg with my 16.5 Smokercraft 90 HP 2 stroke Carburated Mercury Outboard.

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It all comes down to a matter of physics.

It takes more force to push a non-aerodynamic boat across the water than a car on the road. Compare the rolling resistance of a tire vs the surface tension of a boat on water. It just takes more force.

Now add in the “getting on and off plane” factor of plowing water and it just makes it worse.

Maybe some type of gearing could be added to the transmission to reduce the RPM’s. Other than that I don’t know what else you could do.

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I have also wondered why they have not yet come out with multiple speeds for outboards? Not only could you improve top end mileage by doing this but you could also troll at lower speeds! Maybe it would make the lower unit too bulky? confused

Maybe I shouldn't be advertising the idea?

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PDOGG,

That has been thought of many times. I was wondering that back when I was just a little kid. Who knows if anyone has ever tried it though.

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My 140 hp can cruise out 10 miles at 30 MPH, troll from sun up till sun down. Then cruise back 10 miles all on 10 gallons of gas.

140 hp I/O Mercruiser my friends. grin

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Quote:
Maybe some type of gearing could be added to the transmission to reduce the RPM’s.

If I am right, changing the pitch on the prop get gain or drop RPM's

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Theres one reason you can't sift gears with an outboard. The outboard at WOT should stay close to the max RPMs. Anything less and you start to bog the engine and damage it. So you can't except to cruise at 40 MPH and have RPMs around 2k RPMs like you can in your car.

When your close to that max RPM at WOT you'll have your best performance and of coarse you choose a prop to get there.

Heres what you can do to save gas. Slow down!

If your running at max RPMs of 6000 and at a speed of 45 MPH your burning gas at the fastest rate.

Slow the boat down to say 4000 RPMs and cruise at 30 MPH.

Your going to burn a lot less gas and, no your not dogging the outboard because that lower RPM is at cruising speed not WOT. Big load difference between the two.

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There are Controllable Pitch Props. Props that change pitch for changing loads on cargo ships but I have seen them on smaller scale though. You won't see them on a pleasure boat though.

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5,200 Rpms on that motor is close to wide open. You are going to suck gas. I have an older 110 Evindude. If your pulling kids or operating WOT the gas is gone quickly. I can burn 18 gallons of gas before extremely fast pulling the kids. Boats are not fuel effecient when operated at wot.

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Great points Dtro. I think that another very important element to this discussion should be about speed and acceleration. Think about a boat similar to driving your car. If you gunned it at each stop light and screamed around the highways at close to top speed, your car would get crappy mileage too.

I know that you don't want to push water while getting up on plane, but most folks gun it from a dead stop. IMO, you just need to pop the throttle when you're just below getting on plane (starting to push water). Plus, boats racing across wide expanses at WOT doesn't help out fuel economy either.

One last point is that boats have gone to the point of SUV's. Boats these days have so many accessories, 3-4 batteries, extra motors, the list goes on and on. If you're driving the SUV of boats then maybe you need to consider downsizing to the Camry or Cavalier of boats.

Just a few thoughts.

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You want to see a boat that burns up some gas. Take a ride with Deitz! He told me one trip across Chisago at WOT (about 1.5-2 miles) is just over a gallon. (Should be noted that WOT in that boat is about 75 mph and peeling the skin off of your face!)

My boat on the other hand, gets pretty decent mileage. I can run at least 8 miles on one gallon. But I am also running a 14' Lund with a 15 horse.

Skunked's point about not running the escalade, but rather the cavelier is on track. But if you can buy the big boat, you better be able to buy the gas too. It is important to keep up on your boat maintenance as well to optimize your fuel mileage. Keep things clean, organized, and well lubed. Not only will it run better, but it will last longer too.

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Fuel economy on a boat is basically the same as a motor vehicle. If you want 40 MPG from a vehicle you run a compact with a 4 banger and then drive in a sensible manner. If you have a truck and tow the Pro V then it's 10 to 12 MPG. Same way with a boat. If you want to run all day on 6 gal of gas get a bare bones14 footer with a 15 Hp four stroke. The more weight you add and the bigger the HP the more fuel you burn. The EFI 4-strokes with the proper prop and trim are a lot more efficient than the old carbed smokers.

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I have a 1825 proguide with a 90 horse 4 stroke and last I checked 5.8 mpg and thats running wide open from hastings to the boom site above stillwater and back slowing only for no wake zones

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Fuel economy in a boat probably matters more if you go long distances. If you're cruising shore to shore on Mille Lacs, Leech, or LOTW, then I could see fuel economy being a big concern. If not, then buying a fuel efficient rig will not give you a lot of financial gain. Unless of course you just want a new boat smile

You certainly can do better than 3-4.5 mpg at planing speeds with a different boat and motor. You'll give up beam width, some comfort, and some top end though coming from a Pro-V. I've got a new Lund Rebel XL SS (84" beam) with a maxed out 75 Yamaha 4S fuel injected. I was seeing maybe 6 mpg at plane (~ 3400), and the motor is still fairly tight. I expect to see between 7-8 when it's all broken in. As with all boats, I probably drop mpg considerably if I'm at WOT. Good low end and respectable top end, 40 mph. The difference in fuel economy is from less weight, narrower beam (less resistance in water), and the fuel economy from the 4S fuel injection.

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My 40 hp Evinrude VRO (1991) gets me I would guess somewhere in the 5-7 mpg range, one lake I fish is 9 miles long and I can go end to end (WOT) and troll all day on 6 gal of gas. This is on an '89 Lund Rebel 16'

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Go up river and drift down, you've just doubled your mileage! grin j/k

I've always wondered about this as well, but thinking about high school physics, is that when one pushes on the ground it pushes you back. When it comes to water, when one pushes on water it gives and you push into/through. That part is for the prop. In order to go in one direction you have to push in the opposite direction with a force greater than the force of resistance and generating an opposite force that propels you. Water is just not efficient in generating an opposite force to propel you.

The other part is aerodynamics. The higher the wall on your boat is and if you have a double console or full windshield on, it catches air. The more blunt and heavy your boat is in the water, the more it plows through water. Just think, walking quickly on a sidewalk is pretty easy. Walking in knee deep water takes a little more work. Walking through waist deep water is kind of slow as you plow through water.

That bass master magazine was an eye opener for me. I was naive thinking that my boat has a 32 gallon tank, twice of that of my car. But after seeing those mph numbers for boats...I don't need to WOT unless it's for emergency.

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LOL

Quote:
You want to see a boat that burns up some gas. Take a ride with Deitz! He told me one trip across Chisago at WOT (about 1.5-2 miles) is just over a gallon. (Should be noted that WOT in that boat is about 75 mph and peeling the skin off of your face!)

I dont run at WOT often, but its about just under one gal per min if I had to guess.. But thats a MER 250 XS Racing Eng. I get just under 5gpm at abou4400 RPM's I think, but would have to check my smart gauges to be sure.

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My/my grandfathers boat is a Lund Rebel 1650 with a four stroke 30hp that gets pretty good milage. I don't know the distances, but on winnie by my self i fished two days, I was staying at Nodak and went to highbanks and then west of the gap, and back to nodak, then the second day to highbanks and back, plus a little bit of tooling around between drifts, on less than a 6 gallon tank of gas. I was close to empty, and i had another tank with to switch to, but i thought that was pretty good.

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Deitz- I gues we have to pay to play! At WOT you use almost 60 gallons per hour.

I think that the hull effeciency has a lot to do with this question, and different hulls are more effecient at differing speeds, Dietz's hull is probably a pad vee design and will run up on the pad when planed. That minimizes the wetted area and subsequently the drag. At some point after planing and before WOT there will be a maximum effeciency where the best MPG will be attained. Every boat will be different, but they will all see this type of curve. The boat in my avatar was a modified tunnel with a stepped pad and it saw maybe 2.5 MPG at WOT(6100 rpm) and just over 80 MPH with a 29" chopper. Best mileage was at about 3/4 throttle when planed up on the pad with a little assist from lift in the tunnels. At more moderate throttle, the water drag in the tunnels dropped the effeciency considerably.

All "Vee" type hulls that do not have a pad will see the best mileage at about 3/4 throttle with the motor trimmed slightly but not too much. You want to have the boat planed to minimize the wetted area drag and keep the motor in the upper midrange of it's rpm curve. Remember, increasing speed takes exponentially more power and power uses fuel. Fuel = money, and speed is equal to money squared.

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Very good post hydro... On a side note, My father when I was younger was a hydroplane driver. He drove mostly 280 and 145 class boats, but owned a 7liter for a while.

And you are correct on your assumtion of my boat.. I own a BassCat Puma.

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Deitz,

Your boat sounds like quite a rig!

Did you ever get to drive any of those hydros? A 7 liter boat would be an awesome ride! My screen name comes from the boats that I had in the'70s. I was involved in a local racing club and ran a 9' Pabst hydro with a 20 ci Champion Hot Rod, in B stock. It was a blast to run at 50+ mph 6" off the water and close enough to the next guy to touch them. In the '80's I owned the national champion Karelson boat that took the titles in '77 and '78 in A stock.

Today I've slowed down a bit and run a 20' Viper F/S with a 200 Merc EFI. It's a recessed pad hull and runs in the mid 60's, while seating 5 people comfortably and providing a nice fishing platform. Some things change while some things stay the same. Here's a picture......

Image008.jpg

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Fun stuff Hydro, I was too young when my dad was racing. I did go to all the races though, a few of the races we went to had the small outboards you talk about. them things looked wicked!

here is my ride.

IMG_0697.jpg

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Yea, Some of those little boats were just plain wicked rides. Onr of the guys in our club had a D mod rig that was always a show. The boat was a 12' hydro with a 40 ci modified 4 cylinder Mercury running on methanol and turning 1:1 gears. It would do almost 100 MPH. All of those boats had a manual spark advance that you would retard a bit to get it running, then push to full advance as it was opened up. They were started with a rope and if you had it to far advanced, the motor would fire backwards and almost pull your arm off. The throttles were spring loaded to deadman but had a latch pin to hold them for starting. Well this guy was ready to go and he had the spark advance back and the thottle about half in and pulled the rope. The motor started backwards, revved up and pulled the back end of the boat right under water.

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