# Help! Need high power electric motor for small boats.

Discussion in 'Hybrid' started by SnappingTurtle, Jun 25, 2008.

1. Joined: May 2008
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Location: Germany/Texas

### SnappingTurtleSnapping Turtle

The rowing club where we will be keeping our motorboat is building a new catamaran pace boat with electric motor (they will receive government support if they succeed).

Most small electric motors (trolling motors) available on the market don't offer the speed needed to keep up with the rowers.

They have found a company in Pennsylvania building a electric power head, that is then placed on a Yamaha lower unit.

They claim 9hp from a 24volt power supply. This seems really high to me.

Has anyone here ever heard of, or seen one of these in action?

The company name is “eCycle, Inc. Marine Systems”. They are located in Temple, Pennsylvania.

Are there any alternatives that are on the market that could be used on a very small cat (two people, max.)?

Thanks for any and all input with this project.

2. Joined: May 2008
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### SnappingTurtleSnapping Turtle

I know there has to be more on the market.

I have also found examples from Briggs & Stratton (3HP), Torqeedo (6HP), & Ray Electric (5HP), although the last one is over \$5000, which is a little over the top.

Running twin Torqeedo (6HP) would not help any with the top speed would it? :?:

3. Joined: Oct 2006
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### KaaWanderer

Let's do the math, shall we?

1 hp is about 750 watts. One watt (since we're talking DC) is the current of 1 Amp at 1 Volt.

9 hp = 9 x 750 = 6,750 watts.

Since we are running at 24 volts, this means the current of 6750 / 24 = a bit over 280 Amperes.

I don't think so.

Kaa

P.S. The problem with electric drive is not so much the power, as the low energy density of the batteries. To run fast for significant amount of time requires LOTS of heavy batteries. Given cats' sensitivity to weight, I am not sure that a fast electric catamaran is feasible at the moment. A displacement monohull can afford to carry these batteries, a two-person cat can not.

4. Joined: May 2008
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### SnappingTurtleSnapping Turtle

This is what I suspected.

I told them this one sounded good on paper, but in the real world, with todays technology ...

The old monohull hulls are being phased out because of the wake they throw tends to swamp the other skulls.

5. Joined: Feb 2004
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### QuietboatsJunior Member

Try contacting Steve at Epic outboards at www.oemc.biz. They have high power electric outboards. Good luck with your project.

6. ### Guest625101138Previous Member

If you want to pace an angry 8 with top class rowers then you need something that will do up to 12kts. The rowers are pumping out 500W so 4kW total applied with around 65% efficiency. They have a hull that is optimised for their speed. Is going to be a challenge with battery power.

I felt most pace boats would be for training so 10kts would be a good design speed.

I thought a practical limit in length would be 7m. Still long but the hulls can extend past the cockpit. Aim is to keep total displacement under 1 tonne.

Under these constraints Godzilla produces hulls that are 270mm draft and 430mm beam. The power at the hulls required to do 10kts is 2.75kW. With an efficient prop say 3.5kW motor.

You can get low cost electric motors and controllers to do this from 48V. Motor costs around USD450 and controller USD300:
http://www.kellycontroller.com/shop/
I believe the Ray Electric outboard uses a similar motor.

Now the motor and controller will give say 84% efficiency and the battery say good to 70% discharge under regular conditions. This means you need 6kWh of battery for each hour of operation. Lets say 2 hours at 10 knots would be more than enough based on much less power when just pottering about. So you need 12kWh of batteries at 48V. That equates to 250Ah:
http://www.energymatters.com.au/haz...ry-12volt-240ah-n200-p-126.html?cPath=153_212
Four of these will set you back around USD3000. They weigh 71kg each so batteries will be over 1/4 of the total displacement.

You need to keep the boat light so would be glass/core composite construction. Target weight around 200kg. There are commercially built cats that have close to the required hull shape. I cannot recall if they go up to 7m.

So possible but do not underestimate the cost.

I have done testing on the various components that go into this with a longer term project in mind so I have confidence in the numbers:
http://boatdesign.net/forums/attachment.php?attachmentid=20726&d=1209288392

Rick W.

7. ### Guest625101138Previous Member

This link shows what I believe to be a commercially produced version of what I have described:
http://www.stillwaterdesign.com/pages/25C.html
It would probably require slightly larger hulls due to the weight of the batteries but it would be a good starting point.

You can get light weight lithium ion batteries but they are very expensive and most need to be sealed from water ingress.

Rick W

8. Joined: Feb 2004
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### QuietboatsJunior Member

Rick is good--beat me to it. The Stillwater 25C designs do work well with an electric outboard--lithium Ion batteries do help quite a bit with weight but lead acid will still work if distances are not too great and you don't plan on taking on other passengers. Otherwise check out the new 32' Stillwater. Good luck.

9. Joined: May 2008
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### SnappingTurtleSnapping Turtle

Sorry Guys! I somehow haven't been getting my post notices in the mail. I thought no one else wrote any replies.

The project continues!

This new (for me) information, I will pass along to the scull trainer who is now controlling the purse strings for the project.

Sponsors are in place to cover “all” cost in exchange for exposer. A local electric company & the German government.

Hulls have been ordered, but I have forgotten the name of the manufacture. They build the racing skulls and it could prove to be a new market for them. Sorry again, I will ask.

Early test with plastic cat hulls were disappointing, but proved it was possible. They were about 70% too short.

Batteries are coming from Torqedo.

10. Joined: May 2008
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Location: Germany/Texas

### SnappingTurtleSnapping Turtle

The big problem seem to be the professional rowers. There fast, and during regattas this goes non stop for several hours, with no time for battery changes.

The junior groups and the hobbyist pose no big challenge for off the shelf technology available at the moment.

The larger automobile companies are also moving quietly into this sector here, under names other than the ones we know them by. They have expressed an interest, but only in the upper power ranges. Big motors, big boats, big wakes.

There seem to be a lot of middle ground being forgotten in this sector at the moment.

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