Electric Outboard for 25 Foot Boat

[tomlarkin]

I'm looking into installing an electric outboard motor into my 25' Devlin Godzilla (http://www.devlinboat.com/dcgodzilla25.htm) as the primary propulsion. This forum has some old threads on the subject but not about outboards, and many of the links are dead. I don’t want to discuss cost too much here, just the practicality of the idea.

I’m looking at two companies that make electric outboards: Outboard Electric (http://www.outboardelectric.org/index.html) and Ray Electric (http://www.rayeo.com/index.html). Both of these motors are about 5 HP at 60 volts, which they say translate to about 9 HP in a gas outboard. That should be enough to push my boat at 5 knots on calm water for about 6 hours, or about 30 miles.

There are two approaches to electric outboards – submerged motor (Outboard Electric) and air-cooled motor (Ray Electric). The submerged motor is cooled by the water but has higher drag because the submerged area is larger. The air-cooled motor is cooled by a small fan and has a larger ‘head’ at the top where the motor is located. I assume it’s somewhat less efficient because it needs gears to transfer the motion.

The Godzilla is designed as a slow displacement boat, with a fairly flat bottom and a hull speed of about 6.4 knots. It’s designed for a small diesel inboard located about center fore and aft. Replacing the inboard with batteries will end up being approximately the same weight, located in about the same location, so the boat will float as designed. Most of the use will be slow day trips of 2-5 hours on a lake or in protected salt water. The dock has power to recharge the batteries overnight.

For greater distance, Valence Technologies (http://www.valence.com/ucharge.asp) now has a 12 volt Lithium-ion battery that replaces lead-acid batteries. It’s supposed to have twice the power and weigh a third less. It also recharges faster. That would give about a 120 mile range on a single charge. They’re probably very expensive, but battery technology is advancing rapidly so in a few years they should be reasonably priced.

The advantages of electric propulsion are: silent propulsion, no fuel or exhaust smells, high reliability, low vibration, and possibly lower ecological impact, although lead/acid batteries have a lot of nasty stuff in them. If you ignore the purchase cost of the system (big if), the cost for the power is probably lower also.

Disadvantages: initial cost, weight of the batteries, low power, very slow refueling/recharging (overnight), replacing batteries.

For my use, does this seem at all practical? What would you say are the things that should make me kill this idea? Which outboard of the two (or another) would you choose? Any really good sites or books on the subject?

[boylesboats]

I'm looking into installing an electric outboard motor into my 25' Devlin Godzilla (http://www.devlinboat.com/dcgodzilla25.htm) as the primary propulsion. This forum has some old threads on the subject but not about outboards, and many of the links are dead. I don’t want to discuss cost too much here, just the practicality of the idea.

I’m looking at two companies that make electric outboards: Outboard Electric (http://www.outboardelectric.org/index.html) and Ray Electric (http://www.rayeo.com/index.html). Both of these motors are about 5 HP at 60 volts, which they say translate to about 9 HP in a gas outboard. That should be enough to push my boat at 5 knots on calm water for about 6 hours, or about 30 miles.

There are two approaches to electric outboards – submerged motor (Outboard Electric) and air-cooled motor (Ray Electric). The submerged motor is cooled by the water but has higher drag because the submerged area is larger. The air-cooled motor is cooled by a small fan and has a larger ‘head’ at the top where the motor is located. I assume it’s somewhat less efficient because it needs gears to transfer the motion.

The Godzilla is designed as a slow displacement boat, with a fairly flat bottom and a hull speed of about 6.4 knots. It’s designed for a small diesel inboard located about center fore and aft. Replacing the inboard with batteries will end up being approximately the same weight, located in about the same location, so the boat will float as designed. Most of the use will be slow day trips of 2-5 hours on a lake or in protected salt water. The dock has power to recharge the batteries overnight.

For greater distance, Valence Technologies (http://www.valence.com/ucharge.asp) now has a 12 volt Lithium-ion battery that replaces lead-acid batteries. It’s supposed to have twice the power and weigh a third less. It also recharges faster. That would give about a 120 mile range on a single charge. They’re probably very expensive, but battery technology is advancing rapidly so in a few years they should be reasonably priced.

The advantages of electric propulsion are: silent propulsion, no fuel or exhaust smells, high reliability, low vibration, and possibly lower ecological impact, although lead/acid batteries have a lot of nasty stuff in them. If you ignore the purchase cost of the system (big if), the cost for the power is probably lower also.

Disadvantages: initial cost, weight of the batteries, low power, very slow refueling/recharging (overnight), replacing batteries.

For my use, does this seem at all practical? What would you say are the things that should make me kill this idea? Which outboard of the two (or another) would you choose? Any really good sites or books on the subject?



Have you seen Glen-L Marine? Maybe this may help some...
http://www.glen-l.com/designs/special/lovoltage-notes.html
http://www.glen-l.com/designs/special/electricdrive.html

[tomlarkin]

Have you seen Glen-L Marine?
Yes, I've seen those, thanks. I don't want to kludge something together. I'm not a marine architect or an electrical engineer. I'd rather go with a company that has already worked out the bugs and offers a warranty. And I don't want to poke holes in the bottom of my boat :-)

[Ron Carter]

Google Elco Electric Boat. They have several pre engineered systems that might be of interest.

[TR]

http://www.torqeedo.com/en/hn/home.html

In my opinion none of these offer enough power for the boat. Maybe three or four of them :D

Tad

[Mike Vogdes]

Here's one that may intrest you..

http://www.thunderstruck-ev.com/sailboatkit.htm

[RonW]

Hey Tom, I think your math is wrong on the power requirements.
And your last sentence, is this practical for this boat, I don't think electric is practical at all for this boat.

I take it that you are eliminating the shaft and wanting to set the boat up with a well and outboard as devlin did on the gadzilli a 16 fter, even there he used a 20 horse outboard.
You would proably want a 50 horse 4 stroke in a well, that little ray's electric outboard at 5 horse will probably not push that boat more then, if 4 m.p.h. let alone knots.
And even at only 30 mile range, when you step up the power the battery pack will be around or over a 1,000 lbs. It takes 30 lbs of lead acid batteries to replace one lb of gasoline.

That little 5 horse elect. outboard is neat, but not enough power and prop for a big burdensome boat like this. A 24 ft. electric launch are very sleek hulls, not burdensome hulls, and have shafts with larger props and a high torque motor mounted inside with gear ratio to swing that prop. Even then they only run 6 or 7 m.p.h. and maybe 60 miles, but that takes around 1200 lbs of batteries.Or a couple grand in batteries, multiply that by 10 for lithiums.And some of these lithium packs have melted down and blown up, most e.v. people are still relying on old faithfull deep cycle lead acid.

Go with a 4 stroke in a well, and a 20 or 30 gallon tank and have plenty of power and range. Elco can sell and design you a complete system, but it will be set up on a shaft, and cost a lot more with less power and range. A large 4 stroke in a well running at half throtle will be very quiet as well. Simpler, cheaper, more power, more range.

[Pierre LaRochelle]

Tom,
This particular Devlin design screams for a Diesel Inboard! In Tugboat fashion it should be overpowered and capable of yanking the fiberglass Mcyatchs of the week-end warrior class off mud flats, sand bars, and even those stuck between pilings and the like. Make sure you have a well anchored "H" Bitt to belay your hawser to.

Sincerely,

Pierre

[Thorne]

If you are looking for a turn-key solution, go for the inboard or outboard powerplants.

If you want electric it will involve quite a bit of customizing and learning -- but might be worth it (although more expensive than the stock solutions).

This Yahoo group gets into very involved electric installations -
Subscribe: electricboats-subscribe@yahoogroups.com

[tomlarkin]

I think your math is wrong on the power requirements.
RonW - thanks, I looked at the battery weight a little closer and realized you're right. 1000 - 1200 additional pounds in the boat is way too much. I just happen to own a 45 HP Honda 4-stroke, so that's what I guess I'll power it with. The idea of silent oderless travel just sounded so nice there. Maybe I'll put a Torqeedo Cruise (http://www.torqeedo.com/en/hn/products/cruise/product-description.html) in as a kicker and to sneak up on the birds. That's only 100 pounds of batteries, but I bet they're crazy expensive. Maybe in five years I can repower with a practical electric system.

[mcdenny]

Electric conversions of 25 - 35' sailboats are becoming more common. They would have equal or more displacement on similar waterlines but are probably a little more slippery than the tug design.

A typical power system is a 48v, 100 amp (about 6 hp, thunderstruck kit is an example) "inboard" motor turning something like a 12 x 8 prop through a 2:1 belt drive. Cost of the parts (all but batteries) would be around $2k. (8) 6v lead acid batteries are from $500 to $2000 depending on type.

With 500 lbs of batteries you could go 6 mph for 5 miles or 4.5 mph for 10 miles or 3.5 mph for 17 miles. Virtually unlimited range at 3 mph with a little Honda super quiet generator. Doubling battery bank gives a little more than 2x the range at a bit less speed (extra 500#).

Is this practical? Depends on your priorities. Want to go far and/or fast? No. Want to listen to classical music and have a pleasant picnic while cruising around the lake? Absolutely.

Cost is about the same as a new 25hp high thrust Yamaha 4 stroke OB, probably cheaper than a 25 hp diesel installation. Using regular golf cart batteries that have to be watered saves a good bit of $ over AGM batteries.

PS: I don't know of any good books about electric power; most common one (by Doug Little) is pretty basic.

[geeman]

Electric works for the wife and I because our needs are simpler.We wanted quiet and was willing to settle for slower travel and shorter distance.We're not in a hurry when we're on the boat.We like the idea of just cruising slowly along listenning to the radio and being able to talk without raising our voices.We hear enough noise at work,when we're on the water we want QUIET.