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Old 14-03-2010, 03:54   #1
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Electric Outboard - Time to Change from Petrol !

The old trusty mercury 2.5hp 2 stroke is nearing its reliable end. After a lot of web searching I have decided we will give an electric outboard a go. As it is mostly used as a tender from shore to the mooring and then while cruising as a means to reach the near shore. We thought a electric OB would suite and finally we can toss the petrol tins that were always a concern We will get an eBay cheapie to try out, I noticed there is very few neg comments on the feedback about them, so they must work reasonable well out of the box (a heck of a lot cheaper). As for longer cruising, well time will tell, would love to not take petrol at all as it ends up residing on deck (we will not have petrol inside).

We were wondering if anyone has thought up a comparative formula or chart showing HP ratings of petrol versions and the Lb thrust of the electrics. What is the equivalent of the 2.5 Mercury 2 stroke in an electric OB ?
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Old 14-03-2010, 05:13   #2
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I wouldn't give much credibility to the dearth of neg feedback on eBay.

People generally give feedback shortly after an item is recieved in working condition. Few would withhold feedback the 6-12 months + to really give a fair appraisal on the quality and longetivity of a chinese built electric outboard.

By all means use eBay - just don't rely too much on the feedback.

Cheers,

Simon
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Old 14-03-2010, 11:37   #3
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Can't really speak to the conversion, since everywhere you look the conversions vary wildly. There are posters here that know much more about this comparison, but I like to keep things much simpler.

BUT, one thing ,is that an internal combustion engine's power(HP) is rated at a speed at which I never use my motor. In fact, the place at which this horsepower is rated might be who knows where on the motor.

I would have to say a 9HP internal combustion engine delivers much less horsepower at a slower speed . . . such as the general speed of a sailboat, and in my case quite a bit below "hull-speed", a speed at which it begins taking much more power to maintain or increase. There has to be a sorta sweet-spot where electric and IC engines equal out when an IC engine is running at a somewhat slow cruising speed.

An electric motor at slow speed will have much more torque than an exploding-type engine at a similar slow speed. That amount of torque at a slower speed, if properly used could be used much better than the torque of an exploding engine at the same speed.

Best thing to do, is to just get the motor and see for yourself. If it's a MinnKota motor, look up Kipawa propellers. Evidently these props increase the thrust(pushing power) of those electric trolling motors.

I'm waiting for someone to report how much these propellers help more underpowered 12 and 24 volt trolling motors on a 25+ foot long sailboat.

For me, I'd rather have more battery and less gas on board. Of course, to me, a sailboat moving at 2 knots in dead air is okay.
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Old 14-03-2010, 15:17   #4
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Is electric really better?

I looked at electric outboards and felt that they might have the following problems:-
* High total weight when including battery
* Relatively expensive for "marine" quality
* Always need to keep the battery charged
* No reserve when the volts go
* Limited range

Yes I've found that small petrol outboards can be a real pain in the !## but given that small 2 strokes look to be available new for less than a boat buck I can't see where an electric would win out.
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Old 14-03-2010, 15:42   #5
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my brother has a yamaha one is very happy with it. no noise, petrol fums and lighter to carry around. the only thing is make sure you get a decent battery for the job.

i own a 26ft sail boat and thinking to install an electric engine and a generator. i see a big future in electric engines...
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Old 14-03-2010, 15:55   #6
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outboards are rated at the prop. 9.9 and 15 are the same motor most times just tuned. Due to the fact many lakes have a less then 10hp rule hence the 9.9.
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Old 14-03-2010, 15:55   #7
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Electric Motors and Gas Engines. Our club has been using electric MinnKotas on its boats up to 26 feet. We've used the really cheapy ones that are designed for freshwater that we bought at yard sales and now have a larger thrust saltwater model. They all worked well but care must be taken to keep the battery topped off. For a dinghy to and from your mooring a small battery can be used. To push our 26 footer for a goodly amount of time requires a larger deepcycle with some solar panels to keep it up to top.
We've only used the 12 volt types so far. I think they are great but for long hauls and a lot of motoring I'd use a gas outboard.
Good luck in your choice.
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Old 14-03-2010, 15:57   #8
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I didn't mention that the cheap ones designed for freshwater have all failed within 4 years in the saltwater environment. Our saltwater motor is still working after 3 years.
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Old 06-04-2010, 15:57   #9
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We bought the 55lb el cheapo off ebay, only $152 AUD plus $16 postage.

It has been in use for 2 weeks now and runs well. We use a small deep cycle 22AH sealed battery recycled from a back up system. It powers the dinghy to and from the yacht and will last 2 return trips before we have to recharge it. We have 2 batteries and have one on charge while using the other. These are small batteries that are easy to carry and readily available used from people who service fire and back up systems.

The 55lb thrust is not as powerful as the 2.5 Mercury but is only a little slower. It is however very very quiet and we would not go back to using a gas guzzling 2 stroke again.

The motor is very tall and once it is out of warranty we will cut the shaft shorter, as it is way too tall for our puny dinghy.

Time will tell as to how it copes with the salt water.
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Old 07-04-2010, 11:30   #10
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New update on MinnKota motors. All have failed within 5 years of uncared for use. I believe that the motors will do fine with reasonable care. I would get the saltwater version because it gave us the best service. Once the motor is dunked completely including the control head, water can migrate down the tube and into the motor. This causes bearing failure pretty quickly. This happened to two of ours. The other was left in an inclosed space with lots of moisture for a very long time. It suffered the least but suffered catastrophically just the same. One of our club members is installing new bearings.
I think that if not dunked and if kept in a fairly dry space when stored they would last a very long time. Same goes for a small gas engine.
kind regards,
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Old 07-04-2010, 13:25   #11
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I was wondering what the story was with water going down the shaft to the motor. When I take the top off to shorten the shaft, I will look at blocking that tube with sealant.

By the sound of it we should do a fresh water flush before storing it for the winter and put some grease on the shaft, etc.
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Old 08-04-2010, 14:54   #12
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Yes, good idea! As they are from the factory, any water into the control head migrates down the tube into the motor. Definitely not dunkable. You should get more life out of yours with some care.
I really like how quiet they are. Can really sneak up on your neighbors. Yours should perform better than the little engine if you use a bigger battery.
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Old 08-04-2010, 15:02   #13
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I had not tried a big battery as yet, we are waiting for a suitable one to fall in our laps. I have some wet cell LA batts, but want a sealed type as the chances of it falling over are too high.
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