For the mad scientist sailor...

[billwa]

Originally Posted by susswein

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.

I use a 750w 2-stroke cheapie from "bunnings". Was $150. Added a 50 amp charger off ebay for $80. I removed the fuel tank from the gen, and added a Yamaha fitting, so now at least the genny and the outboard drink from the same tank, and the genny can be stored below when fuel disconnected.

[Teknav]

Hold your horses! The "optimum engine output" never exceeds 60%; read-up on the carnot cycle. You also need to take into account the amount of heat being generated, and which cannot be used. It would be nice to have a dynamo's output power continuously re-fed to make the dynamo (turbine) run forever. The laws of Physics do not allow it, in real life. The output is much less than the input, generally speaking. Mauritz

[mr-canada]

Nice to see so many mad scientists jumping into this thread :-)

Ok so I totally understand that the alternator would consume HP, and that that HP would no longer be available for pushing the boat. This is why I proposed a clutch or disengagement of the alternator in the case you wanted all your revs to push the boat.

On my boat I rarely run the 8HP motor past about 1/3 throttle. She hits hull speed at just over that and the motor is more fuel efficient at lower revs for pushing the boat anyway. If I wind it to 90% throttle I might get an extra half knot above hull speed for double the fuel. In theory, for my specific application I've got about 4 of my 8 horses unused most if not all fo the time (seeing as I hate motoring and would rather sail)

As to the specifics. My 2500W 8HP generator example was just from my experience in using generators. Yes it was 120V not 12V. I was guessing at the amps. But I digress.

While I have seen some people pack both a generator and an outboard (and, as some have noted, a battery charger) this is loads of extra equipment and with every interconnection there is not only loss but another possible point of failure. Of course an outboard isnt designed to run a large alternator either so its not going to be the most efficient design, but you will get considerable loss in running a generator, converting that through a charger, and then charging a battery with all those steps in the cycle. Most consumer generators also run a 120V block, so transforming that back to 12V through the charger is also a considerable amount of loss and quite wasteful when you could just generate the 12V off the movement of a motor in the first place.

It is interesting that someone found an alternator option on outboards. I'd love to see a link.

In my particular case my 8HP Mariner is about 20 years old. So if I butchered the cowling and made it look a bit like a mad scientist's creation it would probably make the motor look better rather than worse (LOL). I wouldn't propose anyone who is not a serious professional to hack away at a nice newish Yamaha 4-stroke.

In my own situation I would intend to use such a creation in one of the two following uses:

a) When putting in and out of port or on trips too short to hang all the rags (perhaps a 4HP example), or;

b) When realizing that the battery is low and wanting a charge when shore power is unavailable or at anchor (perhaps using the full 8HP).

I've already got lines run with a 2A fuse from the motor to the battery; but as I said before the 1.5A trickle that comes out of the motor is insufficient to do much charging of a 1000A battery. I'd have to replace the lines (previous owner did some awful work in there) of course if I was putting out any serious amps but this must be doable.

[tamicatana]

it's been done. Go look up "Aqua Bug" outboards

[mr-canada]

I looked up aqua bug outboards and they seem like tiny little chainsaw motors for paddling abouts on lakes.

Do you have any kind of a link for something strong enough to power a sailboat (min 8-9 HP) with the alternator option?

[CruisingFan]

Originally Posted by 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!

+1

[MarkSF]

There's something wierd about your math. 400 hours to charge the battery? What kind of battery do you have? A typical group 24 with be 75 Ah, a group 27 100Ah. That means they'll take 50 hours, and 67 hours, respectively, at 1.5A.

What kind of battery is 1000Ah? I think you are mixing cranking amps with capacity, or do you really have 10 batteries in that boat?

I hate to suggest a simple solution, but how about an outboard with a bigger alternator, or a solar panel?

[Cheechako]

an electric motor replacement for the outboard motor would be cool. Too bad no one makes a bolt-on 120v motor for popular OB chassis'. That and a Honda 2000i would be cool.... Maybe it's too hazardous...?

[Adamante]

Originally Posted by Cheechako

an electric motor replacement for the outboard motor would be cool. Too bad no one makes a bolt-on 120v motor for popular OB chassis'. That and a Honda 2000i would be cool.... Maybe it's too hazardous...?

Wouldn't really be all that hazardous and would, in fact, make a perfect DIY project for the mad scientist type. Any motor with sufficient power for the application could be made to work, as long as it would physically fit within the OB cowling. The only issue I see for a prolonged use as a boat propulsion unit would be providing adequate cooling for the motor within the cowling.

Here's Jamie Hyneman's version of it:

Jamie Hyneman's Electric Outboard Boat Motor - YouTube

[twinboat]

Golden Motor makes some kind of electric outboard kit

[Jimbo485]

Originally Posted by mr-canada

Nice to see so many mad scientists jumping into this thread :-)

It is interesting that someone found an alternator option on outboards. I'd love to see a link.

No link. It is a Yamaha T8PXRD and it is sitting in an outboard well under the cockpit seats.

No mad scientists required, just go and buy one off the shelf.

[Wanderlust]

You don't need a clutch arrangement for the alternator. The regulator on a standard alternator senses the battery voltage and adjusts the current supplied to the alternator field, which controls how hard the alternator works.

So all you need is a switch to disconnect the alternator field wire. This will stop the alternator generating amps (and consuming engine HP). Do a search for Alternator Feed Disconnect for how this works.

When choosing an alternator, you just need to ensure the inbuilt regulator wiring can be accessed, or bypassed and then use an external regulator.

[Adelie]

Originally Posted by 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?

Motorcycle alternator.

[Adelie]

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.

OP was discussing alternate charging source, not alternate drive train.

[Adelie]

Originally Posted by mr-canada

Nice to see so many mad scientists jumping into this thread :-)

Ok so I totally understand that the alternator would consume HP, and that that HP would no longer be available for pushing the boat. This is why I proposed a clutch or disengagement of the alternator in the case you wanted all your revs to push the boat.

On my boat I rarely run the 8HP motor past about 1/3 throttle. She hits hull speed at just over that and the motor is more fuel efficient at lower revs for pushing the boat anyway. If I wind it to 90% throttle I might get an extra half knot above hull speed for double the fuel. In theory, for my specific application I've got about 4 of my 8 horses unused most if not all fo the time (seeing as I hate motoring and would rather sail)

As to the specifics. My 2500W 8HP generator example was just from my experience in using generators. Yes it was 120V not 12V. I was guessing at the amps. But I digress.

While I have seen some people pack both a generator and an outboard (and, as some have noted, a battery charger) this is loads of extra equipment and with every interconnection there is not only loss but another possible point of failure. Of course an outboard isnt designed to run a large alternator either so its not going to be the most efficient design, but you will get considerable loss in running a generator, converting that through a charger, and then charging a battery with all those steps in the cycle. Most consumer generators also run a 120V block, so transforming that back to 12V through the charger is also a considerable amount of loss and quite wasteful when you could just generate the 12V off the movement of a motor in the first place.

It is interesting that someone found an alternator option on outboards. I'd love to see a link.

In my particular case my 8HP Mariner is about 20 years old. So if I butchered the cowling and made it look a bit like a mad scientist's creation it would probably make the motor look better rather than worse (LOL). I wouldn't propose anyone who is not a serious professional to hack away at a nice newish Yamaha 4-stroke.

In my own situation I would intend to use such a creation in one of the two following uses:

a) When putting in and out of port or on trips too short to hang all the rags (perhaps a 4HP example), or;

b) When realizing that the battery is low and wanting a charge when shore power is unavailable or at anchor (perhaps using the full 8HP).

I've already got lines run with a 2A fuse from the motor to the battery; but as I said before the 1.5A trickle that comes out of the motor is insufficient to do much charging of a 1000A battery. I'd have to replace the lines (previous owner did some awful work in there) of course if I was putting out any serious amps but this must be doable.

No need for a clutch, you can eliminate the alternator load by dialing down the regulator for the alternator.