Pontoon Boat & Deck Boat Forum

I'm probably going to get some people who just can't understand why anyone would do this. But I'm an engineering student, so things like this are always flying in and out of head. Just something yall will probably have to deal with around here. Lots of hair brained ideas. Not sure if we have any engineering types around here.

So anyway, I want to put an electric motor in an outboard someday. There are numerous benefits that electric motors have over internal combustion engines. But it really all boils down to this: Gasoline internal combustion engines are only capable of somewhere in the area of 25% efficiency with their energy. In this case the "energy" being gas. The rest is all wasted in heat. Now imagine anything you're doing, anything at all, and you can only do it 25% as well as you normally could. All the rest just turns into heat and heats up the place. Probably a lot more than you want it to. But the electric motor, oh the electric motor, is capable of about 86% efficiency. It makes the internal combustion engine look like the turd that it really is.

A 90hp electric motor, would be more like having a 180hp gas engine, when it comes to your top speed. Which is something that I've noticed everyone around here seems to value. The electric motor can turn double, sometimes triple the RPM's as a IC engine. So right now I can only turn about 5900 RPM with my 90hp Yahmaha. But if I could turn 14,000 RPM, well you get the picture. Over double my top speed. Electric motors also don't really have a power band, and have instant full torque, but I'm not sure how much that would apply to boating.

So now that I've explained why I got this hair brained idea in my head, here's how I'd do it. I'd get some old outboard with no motor in it, that would fit the 90hp electric motor inside, underneath the cover. I'd have to paint the old outboard to make it look nice. But anyway, I'm can see the end of the project, when it comes to that. I'm not saying it would be easy, but I can see the light at the end of the tunnel and how I would get the power from the electric motor, to the prop. Not really all that difficult, just mechanical stuff that may need to be fab'd up, I'm not real sure. Rigging up the motor itself isn't the problem. The battery to run it, is the problem. Well its not really a problem, just expensive. Here it is:

http://www.teslamotors.com/powerwall

Its $3,500. Doing the math on that, it would take me about 50 tanks of fuel to reach $3,500. So after you'd used the equivalent of 50 tanks of fuel, you'd be saving some serious cash. The salesman told me (I know lol) that my Yahmaha 90 should get about 4-7 miles per gallon. The electric motor should get the equivalent of somewhere in the area of 20 mpg. That's a huge improvement. And over the life of the battery, you should see a savings that would justify the cost of the battery itself. If you kept the boat for a really long time, you'd eventually see the entire project pay for itself. I really don't know how long that would take, I haven't gone that far with all my figgerin.


Also there is another option, that would save money, electricity, and weight. Going with an electric motor with half the power. Like this one:

http://www.zuglet.com/ev/fordsiemens/fordsiemens.html

If you did that, you'd still get all the benefits, but it would probably be only equal in performance to my current 90hp Yahmaha, instead of a near 100% increase. You'd still get a top speed increase, cause that smaller motor can still turn double the RPM as your IC engine. Another thing that would dramatically help the project, is merely a rumor. But if true, it would probably push this project from the realm of pipe dream, into something that I'd probably do because it would be well worth it. There is supposedly some company coming out with a battery next year, that would drive the cost of that other battery that I linked, down from $3500 to about $1500. If that happened, well there probably wouldn't be much stopping me. Cause instead of seeing the cost benefits in 10 years, I'd see them in 4 or 5 years. All the while getting to enjoy the benefits of electric motor vs gas engine.

Anyway so there's my weird, and somewhat useless idea. I just think it would be cool to have the added benefits of an electric motor, on pontoon boat.

Almost everyone in my family are engineers, myself, more of an amateur, but i create and repair things in ways other than the way it's suppose to be done. So, with that being said the biggest problem with Engineers is, They always think there the only ones with a specific idea. But anyway, good luck with the project. I love the passion.

Thanks! But yeah I'm sure this idea has been gone over time and time again in lots of different places. Hell some boats are electric motor powered, but I think its all only the bigger ocean dwelling boats. Can't remember. Wasn't really my intention to sound like it was an original idea. I was just thinking that this being a somewhat small forum, (compared to someplace like TheHullTruth) it might never have been brought up around here.

I assume there would also be a great reduction in motor noise.
To me, that is a huge benefit.

I'm just f-in with you, I have to listen to this from my father all the time. I'm just sensitive. Sorry.

Look, 90 HP is 90 HP. You won't spin that prop any faster (and if you could, it would cavitate so much it would be useless).

Yeah, if you turn a prop at 14,000 rpm, you'll either blow the water away from the prop and blow out your gear system, or you'll sink the boat...if not both.

The other thing you'll need to consider is the batteries. How many batteries will you need to power a boat for a full day? How much weight does that add to the boat? How long can batteries last this type of heavy use (In other words, after spending $30k on a new boat, I'm not going to want to spend $5k in 5 years or less for new batteries)?

Wow someone should try this on a car!

Already been done with Submarines.

And with boats:

http://www.evnetics.com/electric-power- ... -assembly/

180 HP electric outboard.



https://m.youtube.com/watch?v=CIJ8e56eEwM

I was an engineer on a diesel/electric ship. Similar to the sub (above) but stayed on the surface and didn't store (batteries) electricity.

Essentially we had 6 diesel engines turning 2 electric motors attached to the shafts/props. Engines attached to generators which pumped electricity to the motors which turned the props. The more demand from the motors (requested speed/RPMs) increased the engine speed to supply required power. At neutral, engines at idle "wasting" electricity.

The reason for this configuration was that the ship was an icebreaker and when a large chuck of ice got caught in the props, all it would do would be to overload the motors, tripping them off line, overspeeding the engine(s) which would then also harmlessly trip off. (We got really good at hitting the engine re-set before it totally died down so we wouldn't have to go through cold-re-start procedures.)

If this was set up with a direct drive/transmission type propulsion and a chunk of ice lodged in the prop, the engine or drive system would self destruct.

The newer icebreakers also use gas turbines (10,000 HP) and variable pitch props in addition to the diesel electric plant.

As far as propulsion for a recreational boat, I don't believe that the weight of the batteries that are now available would prove to off set power savings or be able to produce the energy and/or rpms required to move a boat at anything but really really slow (technical term) boat speed.

That battery I linked weighs the same as a tank of gas. What about a stainless prop vs aluminum when it comes to the pitting and higher RPM? Maybe the RPM could just be limited to 1,000 under the max of the prop for safety, and you could still see some benefits over IC engines. For instance my Yahmaha can only safely turn about 5900, but maybe the prop can a higher RPM than that.

They are right about 90hp is 90hp as far as speed goes. You need X amount of horsepower to push Y amount of load to Z amount of speed. Torque of an Electric engine is great but Torque only figures into the the equitation on how fast you get to X amount of speed. I drive 200-250 Ton Haul trucks in a mine and some of our trucks are Electric drive which have a 2000hp Cummins V16 spinning a generator which supplies electricity to the motors in each rear dual. Actually I'll bring up another powersport comparison. I've got a Yamaha Phazer Snowmobile which has an 80hp 4-stroke that spins 13000rpm and an old Polaris 2 stroke which is 80hp @ 7,800 rpm. Both run the same 75-80mph top speed even though there is a ~5000rpm difference in power bands. The 80 hp Phazer 4 stroke needs geared down to keep the drive train happy but also benefits from the extra torque created by the gearing down which equals faster acceleration. Electric motors will take over some day when batteries get light enough and can store enough energy but that is a LONG way off for pleasure boats. You could have your whole floor covered with Lithium Air batteries but if you were pulling tubes for an hour using all 90hp you have that battery bank would be completely dead where as the gas version would have used a small 6-7 gallon tank. Works ok for cars currently because your average car is only using 8-15 hp to maintain 65-70mph highway speed.

Actually just looked at the math, 90hp is = ~65kw of power. The 3500$ battery back you linked to is available in either 7 or 10kw of storage, so you would only be able to use 90hp for about 6-9 minutes before it would be dead. I have nothing against alternative energies and I truly believe that we do need to make the switch someday but my someday is when my wallet says its OK! Possibly the best "alternative" for a higher HP pleasure craft would be a small 10hp diesel generator charging a battery pack that could supply 90 hp for 5-10 minute bursts and you wouldn't be "left in the dark" when the battery dies as you would still have slow speed propulsion while the battery bank charges back up. That's exactly the type of hybrid car I would want to purchase but no one builds one. A small efficient diesel generator + battery pack would make a sweet commuter car, and the Diesel would supply the heat needed up here in Minnesota during the winter.

I am an electrical engineer who worked in the battery industry at one time.

While on paper your idea has merit, you haven't considered the one factor that keeps electric cars and boats from being an everyday reality. Energy density.

The battery back you list is a 7KWh when used in a cyclic operation. Now that does not mean you can get 7000 watts out of it for an hour. There is a curve on discharge time that in inversely proportional to the current draw. What that means is that you can expect 700 watts for 10 hours. Even if you could get 7000 watts for an hour in one orgasm of discharge, 7kw is not even 10hp. You'll get an hour of puttering around the lake like an old person before its dead.

A gallon of gasoline has about 33.5KWh in energy equivalency. Even assuming 25% efficiency, that gives you about 8.5Kwh if you only burn one gallon an hour. I know my boat can burn more than 10 gph if I whip it hard.

Right now, some of the highest energy density in a commercially available battery in a high-current operation is the common lead-acid battery. a group 42 battery will give about 75 minutes of reserve capacity (Reserve capacity is how long a fully charged battery at 80 degrees will give you 25 amps until it's voltage drops down to 10.5 volts) 25 amps at 12 volts is only 300 watts or about .375Kwh till it is discharged. If you group 10 of them together, you could get a respectable 3.75Kwh for 75 minutes but now you are talking about 280 lbs worth of batteries.

Not saying that it cant be done, but right now, you have to chose between range, speed, or weight

Tim