For the mad scientist sailor...

[mr-canada]

Ok. Here's an idea and I have no idea if it will work or not. Probably would - but the skill level is beyond my means and I have no idea what it will entail.

I have a sailboat with an outboard. The motor puts out a 1.5A charge off the 8HP mariner which is run to the battery. This, of course, would take somewhere in the neighborhood of 400 hours of runtime at 50% throttle to charge my battery. So, for all intensive purposes, largely useless for anything but propelling the boat.

But...

An 8HP *generator* on the other hand, can output as much as 2500W at 15A; more than enough to charge a battery in short order.

Has anyone any ideas on perhaps fusing the two? I am not expecting a Yamaha rep to come on here and announce a new product (although that would be fantastic), rather, what might be entailed in finding a way to attach a solid alternator onto a 2-stroke (or 4-stroke) outboard engine so while you're obviously working the motor harder, you're now generating a respectable amount of power.

Alternators for 12V systems are widely available - most notably for car and truck applications. What might be involved in attaching a decent sized alternator onto an outboard engine.

I think that this might have application for all sorts of cruisers who have smaller sailboats with outboard motors. I love roughing it and all but being aboard a sailboat with no more power kind of sucks - it happened to me last summer on my first cruise with my boat.

It sure would be nice to be able to grab a big aftermarket alternator from the automotive industry, buy a different size belt, and attach it to the block of the outboard with some butchering of the factory cowling, and be able to pull 14V at 3-6 amps off a peice of equipment I already have. I've seen some people lug around a generator, but it seems like duplication when you already have a motor attached to the boat.

Any zany thoughts?

[mr-canada]

and on some further thought, maybe a clutch on the thing - so you can disengage it when you're only wanting to use your motor for forward or backward movement and not waste fuel spinning the alternator

[SkiprJohn]

I see a patent coming?
It would have to be extremely heavy for an outboard to have a generator that'll put out that kind of electric power.
kind regards,

[Kettlewell]

Lots of little gas generators exist that are basically nothing but outboard motors designed to supply power. No need to reinvent the wheel here. Buy a little Honda generator. Sometimes it isn't worth it "butchering" one piece of gear in order to make it perform two functions.

[Lake-Effect]

Originally Posted by mr-canada

It sure would be nice to be able to grab a big aftermarket alternator from the automotive industry, buy a different size belt, and attach it to the block of the outboard with some butchering of the factory cowling, and be able to pull 14V at 3-6 amps off a peice of equipment I already have. I've seen some people lug around a generator, but it seems like duplication when you already have a motor attached to the boat.

Like most great ideas, I think it's been tried. (but I can't find a link) That groove on the flywheel certainly seems quite ready for a v-belt and an auto alternator, doesn't it?

I keep thinking about one step further: a generator producing DC (12, 24 or 36 v) an electric propulsion motor or electric outboard, and a battery bank sufficient for maybe 30 to 60 min of motor running. To me this could bring many advantages:

- Motor optimized for generation
- locating the motor/generator anywhere on the boat
- actual drive motor is smaller and lighter, transmission not necessary to reverse
- easier, faster maneuvering with electric power
- possible recharging from drive motor acting as generator

Current downsides are cost, higher complexity and total weight, but I think that new battery technology could make this feasible soon.

[Kettlewell]

Diesel electric propulsion has been used for a long time on trains and bigger boats. It is a good system, but there is a bigger upfront cost than for a diesel driving the shaft and prop directly.

[marc2012]

Think how when you hook jumper cables from your auto what happens to the motor.Same load would probably stop a yammyammyapyap 8 hp.

[Jimbo485]

Our port outboard is 8 HP for a 40´ cat and comes with a high thrust prop and a 6A alternator. I consider it to be such a small alternator that I don´t even regard it as a source of energy. (Got 50A coming in through the solar panels right now)

If you consider 6 A to be sufficient for your needs, just buy one of these outboards from Yamaha. Yes, they do already make them! Forget about that patent!

[Lake-Effect]

Originally Posted by Kettlewell

Diesel electric propulsion has been used for a long time on trains and bigger boats. It is a good system, but there is a bigger upfront cost than for a diesel driving the shaft and prop directly.

Of course, but if you compare the gen/batteries/electric motor setup with a boat that has both an engine and a genny, the upfront costs start to be comparable.

And most sailboats are ballasted, so the extra weight of a hybrid solution can be designed into the boat.

anyway, it's coming... I believe it will go mainstream once new battery technology comes out.

[denverd0n]

One thing... I hope you don't think you're going to have 8hp to push the boat, and at the same time 8hp to charge batteries. If you could manage to hook up a generator to your outboard, every hp that goes to charging the battery is one less hp that is available to push the boat.

Conservation of energy--it's not just a good idea, it's the law!

[hellosailor]

"Conservation of energy--it's not just a good idea, it's the law! "
Or the appearance of one. My dog never understood how elevators or car worked, either. Our observations and assumptions about physics may be not so different from the dog's.

It would be simpler and cheaper to just sell the outboard, buy an 8hp generator, and hook up an 8hp trolling motor when you wanted it. See? Someone already makes the swiss army knife.

[hpeer]

Well, you could convert to electric drive, then run the generator to charge the batteries to move the boat.

[denverd0n]

Originally Posted by hellosailor

My dog never understood how elevators or car worked, either. Our observations and assumptions about physics may be not so different from the dog's.

I'm willing to bet that your dog never thoroughly researched and exhaustively tested the functioning of elevators. Humans have, when it comes to the first law of thermodynamics.

Now, I won't deny that there is some small possibility that in very specific, very obscure circumstances, our understanding of the laws of physics might be flawed. When it comes to something as simple as attaching a generator to an outboard, though, not a chance. Conservation of energy unquestionably applies.

That means you have a total of 8hp to work with. No more. If you use all of that 8hp to push the boat, then you have zero available for charging batteries. If you use 4hp to charge batteries, then you only have 4hp available for moving the boat. Whatever happens, every hp you use for charging is one hp less for moving the boat. Absolutely no way around that.

[Steve W]

The OMC 15HP 2 stroke saildrives used a 35 amp Delco Altermator option, pretty rare. Ijust looked for some pics, but could only find reference that it was an option, The one I saw years ago on an S-2 had the bracket-mounted alternator driven off the flywheel. No motor cover since it was an inboard.

[susswein]

I think it's a great idea (if it could be done cheaply enough) but I don't get your math:

>>>An 8HP *generator* on the other hand, can output as much as 2500W at 15A; >>>more than enough to charge a battery in short order.

1HP is theoretically equal to 750 watts, so 8HP is 6000 watts. Watts equals amps x volts, so 6000 watts = 500 amps at 12V or 50 Amps at 120 V (this assumes 100% efficiency). I don't know of any car alternator rated at more than 100 amps, so your max charging would be 1200 watt/hours, but would require extra large cables running from the outboard alternator to the battery bank. Your statement above about 2500 watts at 15 amps makes no sense, since that comes out to an oddball voltage of 166 volts. More likely the 2500 watts was at 120V, and the 15 Amps was at 12V. Most generators limit the 12V output as a safety measure, since many users use undersized wire not capable of handling 100+ amps.

A simpler (and probably cheaper) solution that I use is a 1000 watt honda generator and a walmart 40 Amp/120V battery charger. Combined cost (used) was $500, and I'm only running the generator at 50% capacity.