electric outboard as a get home engine

[SCOTTEDAVIS]

Originally Posted by FF

For my bucks the answer would always be HYD.

The noisemaker with a hyd pump could power a cruise generator 6KW , bow thruster , dink crane, windlass and with belts or a chain the main shaft.

For main shaft disaster a wing Hyde feathering prop and hyd motor would be good for as many thousands of miles you have to go.

AS the noisemaker would power the get home its frequent inshore use would give hope that it would start..

A hyd pump on the main could power the 6KW underway , and the rest of the hyd power users should the noisemaker be down.

This might be a pricy retrofit if all done at once , but it is a very KISS way to cruise.

All with no WHITE SMOKE!!

Do you disagree with post #26?

[N4712]

We'll be pulling a 17ft CC with a 115 wherever we go, which is way more then enough horse power. But well probably never have to have to use it to tow the Nordy since we have a wing. But it and the RHIB on the top would come in handy when docking.

[Ski in NC]

Hydraulics can be very nice, but really need to be designed into the boat during construction. Routing pumps, lines, tanks, and valves takes a lot of room. Backfitting an existing boat is a monumental PITA. And leaks will make quite a mess. I think electric drive things are better until the HP requirements get too high to be practical. Little boats better served with electric auxiliaries.

[rjtrane]

I have always felt that the best "take home" system is using the main prop and shaft with some form of power belted to the shaft. A small outboard propeller (or even a small, inboard take-home system with small propeller) will not work as well as the main prop, HP for HP.

If starting from scratch, I'd have a pair of equal generators, each fitted with a hydraulic pump and leading to the hydraulic motor belted to the shaft. The reasoning for the pair of generators is that one cycles them on/off, each a day at a time, decreasing each's hours when living on the hook. For take home, you double the power available to the motor. Of course, if retrofitting, then using what you have works, too.

If you'd like an electric solution (which can have other payoffs), then again, a motor belted to the main shaft. With the right electronics, this motor can act as a generator while underway, saving hours on your main generator. Most likely, this motor will be no less than 48v DC. So you will also need a 48v battery bank along with a way to charge this battery. If starting from scratch, you can install a 48v variable-speed generator to charge the battery and to run the take home motor. DC/DC converters supply your 24v & 12v needs - the inverter(s), your 120VAC & 240VAC needs.

I'd suggest no less than 6 kW motor. This is 8 HP, but a really GOOD 8 HP full of torque. My guess is you'll get 4 knots in calm seas and the same maneuverability for when you do get home. Obviously, your generator should be at least 6 kW or more for sustained motoring.

The Torqeedo 4 kW OB uses a 48v battery and may have enough oomph to steer and get you home. You still need th battery and the way to create the electricity, either with a 120VAC/48v DC charger or 48v generator.

If you go electric, most likely you will make your ships service battery 48v. And, if it's in the budget, go LiFePo for the battery. If not, you do need AGM to handle the flow of current through the battery from genset to motor.

Outback makes good 48v/120VAC inverter/chargers - 100A charger (about 5kW?).

[healhustler]

Reubin: When you're speaking about belting "to" the shaft to utilize the main shaft and prop (as pointed-out by Eric earlier as so much more efficient), how do you compensate for the lateral loads? I'd be pulling against one side of my transmission bearing and seal, and also against my shaft log, seal, and eventually my cutlass bearing. I've used slide-on center-bearings on lots of things, but not with anything that requires such precision engine alignment. I understand we are talking about "get-home" emergency applications here, but at least part of the system would need to be kept on the main shaft and balanced correctly, even if the belt just hung loose on a separate adjustment pulley.

[rjtrane]

There exist a variety of systems in the electric hybrid world that essentially insert themselves between the output of the diesel and the shaft - of course, the shaft would need shortening and machining to allow for the space required. These can have a clutch, also, to disengage the electric motor from the shaft and/or disengage the diesel motor from the shaft.

To answer your question directly, I would assume the installation of a bearing fore and aft of the belt would be a good idea. I'm not sure how much side-load a cog-style or chain might have? Out of my expertise.

If I were doing this, I would make it not just for emergencies - but use the engine HP for generating electricity underway, much the same way my parallel hybrid does. And, one can use the electric motor for in-harbor maneuvering and/or cocktail cruises (assuming enough battery or a very quiet generator).

[denverd0n]

Originally Posted by manyboats

The expression "get home" is not really not "the point". It's getting to any safe place.

See, I think this is key. You have to fully understand what you expect from your "get home" alternative. Do you just want something that can get you out of danger and to the nearest safe place to effect repairs? Or do you expect your "get home" alternative to be something more like "allow me to continue my voyage if the main propulsion fails"? It seems like there is a big disconnect between the people who use the term "get home" more in the latter sense versus in the former.

[RT Firefly]

Greetings,
Hmmm....47 posts and not too much thread creep? This will never do....
First Porsche-Designed Car from 1898 on Display at Porsche Museum
Well, it IS electric!

[healhustler]

Originally Posted by rjtrane

If I were doing this, I would make it not just for emergencies - but use the engine HP for generating electricity underway, much the same way my parallel hybrid does. And, one can use the electric motor for in-harbor maneuvering and/or cocktail cruises (assuming enough battery or a very quiet generator).

That might be an eventuality for me. I meager study the systems available could gain the staunch support of my Admiral, who is in favor of anything that would silence the boat.

[Wxx3]

Originally Posted by rjtrane

I have always felt that the best "take home" system is using the main prop and shaft with some form of power belted to the shaft. A small outboard propeller (or even a small, inboard take-home system with small propeller) will not work as well as the main prop, HP for HP.

If starting from scratch, I'd have a pair of equal generators, each fitted with a hydraulic pump and leading to the hydraulic motor belted to the shaft. The reasoning for the pair of generators is that one cycles them on/off, each a day at a time, decreasing each's hours when living on the hook. For take home, you double the power available to the motor. Of course, if retrofitting, then using what you have works, too.

If you'd like an electric solution (which can have other payoffs), then again, a motor belted to the main shaft. With the right electronics, this motor can act as a generator while underway, saving hours on your main generator. Most likely, this motor will be no less than 48v DC. So you will also need a 48v battery bank along with a way to charge this battery. If starting from scratch, you can install a 48v variable-speed generator to charge the battery and to run the take home motor. DC/DC converters supply your 24v & 12v needs - the inverter(s), your 120VAC & 240VAC needs.

I'd suggest no less than 6 kW motor. This is 8 HP, but a really GOOD 8 HP full of torque. My guess is you'll get 4 knots in calm seas and the same maneuverability for when you do get home. Obviously, your generator should be at least 6 kW or more for sustained motoring.

The Torqeedo 4 kW OB uses a 48v battery and may have enough oomph to steer and get you home. You still need th battery and the way to create the electricity, either with a 120VAC/48v DC charger or 48v generator.

If you go electric, most likely you will make your ships service battery 48v. And, if it's in the budget, go LiFePo for the battery. If not, you do need AGM to handle the flow of current through the battery from genset to motor.

Outback makes good 48v/120VAC inverter/chargers - 100A charger (about 5kW?).

Thanks.
Since I am not starting from scratch, I don't want to do a lot of modifications to my current propulsion system, as it works quite well as designed.

So, an outboard stuck on the swim platform with plywood and sheet metal screws could be an answer.

My point is I'm thinking of a one time let's get anyplace where real repairs can be affected.

And my five f... gallons of gasoline won't be enough.

A diesel outboard seems to be the real solution for what I want.

Will probably look at that again (or do nothing) , but I asked the question to make sure there was not something I was missing.

Richard

[FF]

Do you disagree with post #26?

Yes and no , a 10 HP anything is not going to give sterling performance to a 15-20 ton boat, even with a perfect engineered Hyd installation.

The boat with a larger engine that had poor performance could probably be there was installation , but ZERO engineering on the hyd system.

For minor power 2-3 HP for a short time , it is far simpler to stick in DC electric power for the thruster or windlass.

Once the power is 10+ hp electric would seem to be out of the picture.

Big buck folks could run 240 or 440V to a hyd power pack and it would work fine , but the expense would be huge , with the only advantage being easier to retrofit.

Hyd can NOT be stuck in willly nilly as another layer of electric wiring.

It must be engineered , and as with electric there are any number of OK systems.

[healhustler]

When I read threads like this, I imagine guys like Ken Fickett (Great Harbour Trawlers) must be quite entertained. His twin Yanmars, decent sized rudders and huge engine spaces pose a strong argument for good, service-able twin diesel installations with reasonable single engine handling, specifically in reference to "get-home" security. A fuel polishing system and a day tank with separate filters for each engine would pretty much take care of it.

Youz guys already with twins know that all twin boats aren't equal when it comes to single engine handling, but in all but the worst case scenarios you can probably maintain a fair compass heading toward something.