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Old 02-12-2019, 14:38   #31
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Re: Gemini 105mc conversion Diesel to EV?

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Originally Posted by Mr B View Post
The Sonic drive has now stopped production,
They still have spares for it, But not sure how long they will last,

My Westy 30B uses 3/4 US gallons per hour,
Its a Mitsibishi engine, Buy one from a Mitsubishi dealer ( Tractor dealer) and put your existing heat exchanger on it,

Heat exchanger replaces Radiator, = Marinised,
Thatīs right and go sailing in 2-3 weeks with a sweet new engine if that is all it takes.
Any decent farm garage can handle this job.
And with the saved money upgrading the boat to fair market value.
Here check it out... brand new in Germany 3500 $.
https://www.motorencenter.de/industr...-neumtor-im-at
and here factory rebuilt 3100 $
https://www.motorencenter.de/industr...ohne-pto-im-at
Canīt be much more in the USA
For that money I would not even bother to repair. Hell with the Marimafia the labour alone might cost more.
That should give him some 10-15.000 $ to play. Goes a long way on a Gemini if You know what You are doing.and donīt have two left hands.
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Old 03-12-2019, 01:36   #32
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Re: Gemini 105mc conversion Diesel to EV?

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Thatīs right and go sailing in 2-3 weeks with a sweet new engine if that is all it takes.
Any decent farm garage can handle this job.
And with the saved money upgrading the boat to fair market value.
Here check it out... brand new in Germany 3500 $.
https://www.motorencenter.de/industr...-neumtor-im-at
and here factory rebuilt 3100 $
https://www.motorencenter.de/industr...ohne-pto-im-at
Canīt be much more in the USA
For that money I would not even bother to repair. Hell with the Marimafia the labour alone might cost more.
That should give him some 10-15.000 $ to play. Goes a long way on a Gemini if You know what You are doing.and donīt have two left hands.
Wish I'd thought of that before spending $3500 having my Northern Lights generator engine (Mitsubishi L3E) head rebuilt after poor installation caused sea water to sit in the exhaust and then corrode the valves. Especially since a year after the crank failed and I spent around $10000 on a new Westerbeke to replace it.
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Old 03-12-2019, 01:52   #33
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Re: Gemini 105mc conversion Diesel to EV?

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Hello All,

I am curious if anyone has converted a Gemini 105 to EV yet? I am asking because yesterday I went and walked 1996 Gemini 105 that needs a bit of work, but within the price we talked about is looking to be a decent starting point. I know there are many videos of people scraping the diesel engine in favor of a gas outboard, but with my background of building electric bicycles for fun and owning a tesla model 3, the idea popped in my head of going the EV route. While looking at the boat, the owner was able to start the diesel engine, but it ran very poor and shook pretty violently and while looking at it i noticed there was a leak coming from the side of the engine block and closer inspection appears to be a hairline crack in the block of the engine near the head, so the engine is shot basically. After talking to the owner about that and a few other things i noticed, he threw out the price of 35k on the purchase and i told him i would get back with him after giving it some thought and also told him i gotta talk it over with the other half (don't have a other half at the moment, so a bit of a fib), but just wanted to buy time to think this over.

So the idea i was thinking was pulling the diesel engine, but leave the prop head and attach the electric motor to it for propulsion instead of re-inventing the wheel completely. I also looked into the company i buy my electric bike motors from and they offer a 96v 50kw max/25kw continous Motor/Controller kit for $2400, which could be combined with 4s x Tesla Model S battery modules for bare minimum battery pack for $3600.
We had a 1996 3400...switched from 40hp outboard to 25hp. Some have gone down to 15hp. In normal conditions 15hp works but we've been flat out fighting strong winds only able to make about 3kt headway with the 25hp...so would argue the 25hp is a nice sweet spot for enough HP without overkill.

In calm conditions, it doesn't take a lot of power to hit 4kts...if you want to get up to more typical cruising speeds for a gemini (6-7kts) it takes a lot more power.

They are small boats, so throwing a 1000lb of battery on the stern will push the stern down noticeably. If you just want to get out of the marina until the sails are up, this is very much viable. If you want to cruise 50 miles in 7-8hr under power...much more difficult.
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Old 03-12-2019, 01:53   #34
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Re: Gemini 105mc conversion Diesel to EV?

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If the engine is bad how is the rest of the boat as it pertains to sailing?
I could be wrong but believe the drive was through a leg. I've read have problems hence the OBs.
FYI
A lot of people have converted to outboard due to the wonky stillete drive leg. That's one reason we went with an outboard version.
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Old 03-12-2019, 02:17   #35
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Re: Gemini 105mc conversion Diesel to EV?

This might seem stupid and I don't know the boat but what about installing 2 x 9.9hp Yamaha high thrust outboards. Lots of much bigger cats make do with these. Installing 2 would mean they won't need to be steerable so could be installed a s far apart as possible.
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Old 03-12-2019, 02:21   #36
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Re: Gemini 105mc conversion Diesel to EV?

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This might seem stupid and I don't know the boat but what about installing 2 x 9.9hp Yamaha high thrust outboards. Lots of much bigger cats make do with these. Installing 2 would mean they won't need to be steerable so could be installed a s far apart as possible.
It's been done but the boat is already set up so the outboard/drive leg is steerable.

There's only room to get twin outboards about 6ft apart, so working them against each other isn't as effective as on wider boats. Plus once you learn to use the directional thrust by steering the outboard, it's darn near as good as twin engine designs.
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Old 03-12-2019, 22:55   #37
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Re: Gemini 105mc conversion Diesel to EV?

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Originally Posted by storx View Post
Hello All,

I am curious if anyone has converted a Gemini 105 to EV yet? I am asking because yesterday I went and walked 1996 Gemini 105 that needs a bit of work, but within the price we talked about is looking to be a decent starting point. I know there are many videos of people scraping the diesel engine in favor of a gas outboard, but with my background of building electric bicycles for fun and owning a tesla model 3, the idea popped in my head of going the EV route. While looking at the boat, the owner was able to start the diesel engine, but it ran very poor and shook pretty violently and while looking at it i noticed there was a leak coming from the side of the engine block and closer inspection appears to be a hairline crack in the block of the engine near the head, so the engine is shot basically. After talking to the owner about that and a few other things i noticed, he threw out the price of 35k on the purchase and i told him i would get back with him after giving it some thought and also told him i gotta talk it over with the other half (don't have a other half at the moment, so a bit of a fib), but just wanted to buy time to think this over.

So the idea i was thinking was pulling the diesel engine, but leave the prop head and attach the electric motor to it for propulsion instead of re-inventing the wheel completely. I also looked into the company i buy my electric bike motors from and they offer a 96v 50kw max/25kw continous Motor/Controller kit for $2400, which could be combined with 4s x Tesla Model S battery modules for bare minimum battery pack for $3600.
Take a look at fmt-kempen.de
Make it retractable.
And DON'T USE EV-batteries! They are not imanent safe and in case of a thermal runaway they not burn the boat only. Due to temperature above 1.200°C it produces hydrogen gas if it get in contact with water (and there is plenty around). That quickly solves the problem to be toasted slowly...
50 kW is much overpowered! It has more torque than 100hp Diesel!
I plan to go electric driven for a Seawind 1190 or 1260 and found out that 2x11kW + 2x400Ah@48VDC (LFP !!!) + 15kVA genny suits perfect for cruising.
Cheers
Dirk
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Old 06-12-2019, 10:54   #38
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Re: Gemini 105mc conversion Diesel to EV?

Electric power efficiency versus fuel is more to do with large losses of I/C engines .
Roughly speaking the global efficiency of I/C is about ~5%.

The screams from the roof tops are that Diesel engines are 30% efficient can already be heard the far side of the moon .

However when you put the ~ 30% power through the gearbox and then the prop shaft and then the prop the drive train losses are high so ~5% tends to global norm for many small boats
Example is gross 10 HP inboard will after all losses return 0.5 HP net power pushing the boat .

A electric 48 volt power unit using Lithium such as LiFePO4 types might return a global efficiency of ~10% or about double that of the I/C engine
There fore a ~5 HP electric solution might match a 10 HP diesel solution and return the same 0.5 HP global efficiency to the boat to push it along


The problem is power density of Diesel fuel versus battery .

Diesel fuel is about 11.6 kilowatts power per kilo which in global power to a Diesel engine makes ~0.6 kilowatts of power after losses the normal 5% global efficiency

The power density of electric power from Lithium is about 150 watts per kilo at best or ~ 1.5 % the power of the diesel fuel at best
Lead acid is worse again around 50 watts per kilo so less than 1% the power density of Diesel fuel

A example of this issue would be Narrow 4 ton 1970 era mono hull 9 metre boat with ~ 18 HP engine at ~1800 rpm and fixxed two blade prop at about 60% power in Ideal calm waters with no adverse currents would move at ~5 knot and could return ~.1.5 liter fuel used per hour or about ~ 14.5 nautical mpg UK 4.56 liters.
We could say 10 liters of fuel = 7.5 kilos = 10 hours= 150 N miles .

The rule of thumb is 0.4 liters per ton per hour

From the power density of Diesel at ~11.5 kW per kilo we can say for 7.5 kilos fuel makes ~8500 watts fuel used per hour which at ~5% efficiency makes 400 watts global power to work to push boat or about 0.5 HP or 1/2 HP to motor along

Others will say but it was a 18 HP engine so that makes ~1 bhp not 1/2 HP
At 60% gas the 18 HP engine is probably making ~8 HP which with losses will come closer to 1/2 HP

To get electric to give the same range we require 7.5 kilos to be increased a lot closer to ~40 times the weight at about ~300 kg with today's battery types . Also the battery costs go orbital per kilo compared to diesel fuel at $1 a kilo

Therefore the electric boat solution tends to be decrease the range to keep costs and weight issues down .

Extreme boats will choose to use solar panels to keep battery working longer periods of the day and use diesel generators to drive the electric engines at night but most budget cruising boats are better served with diesel only solutions .

Boat craft that always hook into the marina shore power and require short ranges to do a few hours sailing each day can more effectively utilise electric solutions .


Multi hull electric solution are more severely impacted by the the wetted hull issues than a narrow mono is
Effectivly the Cat is two narrow mono hulls .

The experimental Solar craft chose to use Trimeran solution went with one big narrow main hull and two very small outrigger hulls to keep stability and reduce wetted hull issues

Yes electric boat power solutions will one day be best cheapest lightest systems but it looks to be s good few years away if not decades away.

Bear in mind rough waters will reduce both fuel and electric power effecientcy dramatically and diesel engines effecientcy can drop a lot closer to 1%
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Old 06-12-2019, 11:14   #39
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Re: Gemini 105mc conversion Diesel to EV?

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Originally Posted by bouncycastle View Post
Roughly speaking the global efficiency of I/C is about ~5%.
Since the efficiency of an ICE is around 30-37% you're saying 95% of that is lost in the gearbox and final bearings?
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Old 06-12-2019, 11:27   #40
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Re: Gemini 105mc conversion Diesel to EV?

Hi,

I am designing a tesla s powered catamaran myself and I think it is a good idea. Ideal on a cat like the gemini. I would, however, advise against going as high in voltage as you were thinking of. I intend to stick to 48v. And 2 x 10 or 15 kW machines on a 44 foot very light catamaran. I will, at times, quite possibly, be underpowered but the idea is to use the sails as my main propulsion. And honestly I think the occasions where I wish I had more power will be few and far between and probably due to poor seamanship on my part.

48v is a fairly simple voltage to work with. Going as high as 96 has huge advantages in some ways, but drawbacks on the equipment side. Chargers, solar panels and such become hard to find at voltages above 48. I have managed, but struggled, to find options at 48. I believe as you go higher it becomes more difficult. Not at all impossible, but give it a hard look.

I believe you can quite comfortably stick to 10kw, perhaps even less on a small and light boat like the gemini. On the other hand, an electric motor is pretty happy to run on lower power than it is designed for, so having the extra umpf when you need it might be a good idea.

I'm guessing you intend to go with 4 tesla packs. That is 21kW of power. The amp draw to occasionally power 2x50 kw peak is also something you want to think about.

Have a look at these kits:

https://www.thunderstruck-ev.com/ele...oard-motor-ev/

There are many more options out there, but this is a good way to get started.

Wish you all the best with your project! I like it.

/ Axel
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Old 06-12-2019, 11:41   #41
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Re: Gemini 105mc conversion Diesel to EV?

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Originally Posted by mikedefieslife View Post
Since the efficiency of an ICE is around 30-37% you're saying 95% of that is lost in the gearbox and final bearings?
That's how i read the post and I think that figure is grossly inflated.
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Old 06-12-2019, 11:53   #42
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Re: Gemini 105mc conversion Diesel to EV?

Hm, Silent Yachts use a cat, Engergy Observer which is completely run by solar is a cat. So there seems not to be such a big issue with two hulls...
Even the premiere vessel for the launch of Volvo Pentas electric propulsion system is a freakin' Fountain Pajot!
Why is that? Did they all miss something?
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Old 06-12-2019, 12:00   #43
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Re: Gemini 105mc conversion Diesel to EV?

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Since the efficiency of an ICE is around 30-37% you're saying 95% of that is lost in the gearbox and final bearings?

Some losses exist there but props are typically 60% efficient at best .

However best % power and fuel returns tends to be two bladed slow RPM props without keel or rudder or close to hull that makes interference and with prop matched to boat and engine and best cruising speeds .

Add in flat type simplex form folder props smaller faster RPM three or four blades and keel interference and props can waste a lot more power

The 37% efficient diesel engine is when it is new well maintained and other factors .

In ideal calm waters with ideal boats at 50% water line speeds global efficiently can go up to the 10 % regions but for mere mortals ~5% tends to the real world .

There are many variables so it not so easy to say its 6.754% end result so it more like its closer to 5% than it is 10 %

In electric power with amps volts watts and known heat losses in battery to motor chain its more easy to get a closer % result .
Electric power doesn't suffer pulsing losses like piston engines tend to .

Large oil tanker and cargo container ships for example have large slow RPM props
Also thrybtend to work at 50 % water line speeds and have multi story multi piston engines 25 000 hp power that are 50 % efficient and are less impacted by big waves due to their huge size .
Cargo ships use 3 grams of fuel to move 1 ton of cargo one mile
Aircraft will use 600 grams of fuel to move one ton of cargo one mile

Our small craft basically for pleasure and not cargo are hard to rate but the fudge figure seems to be 0.4 liters per ton

That suggests for many small cruisers under power at typical 3/4 water line speeds 5 to 7% in calm conditions is where many of them will exist .

Running diesel engines at slow speeds often reduces their efficientcy.

The throttle setting of 60% to 70% tends to be best returns on MPG for marine diesel engines depending the craft and prop and other factors

That's my understanding the issues
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Old 06-12-2019, 12:02   #44
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Re: Gemini 105mc conversion Diesel to EV?

EV can work, if you are committed to making it work and accepting the compromises. On a Gemini, you will be hard pressed to get even 2KW of solar, so that's your power source. And half of that will be dedicated to house loads (many folks put 1KW on a boat, even with an engine available.) So that leaves 1KW for engine output. A conversational rule of thumb is 3x for daily output (yes, I know, there are 1000 reasons why that's not the actual number, but it's a conversational number). So, you are looking at banking 3kWh/day. Assuming a modest 10kW of motor power (or about 15hp, probably not crazy low for Gemini), that gives you 20 minutes of motoring per day of charging. Even shore power is a concern -- if you use a 30A cord, you'll be lucky to get more than about 3kW out of it. That's 3 hours of charging for each hour of motoring, and that's if the battery can take it that fast (yes, lithium usually can). So if you motored at full throttle for 6 hours, you'll need 18 hours to recharge.



Here's the deal. If you motor out, go sailing, and then motor back, short distances, then let the boat sit on a mooring for a week while it recharges, great. I mean, really, GREAT! Or if you are Sailing Uma and are fine knowing that motoring isn't an option, great. Or if you are retired, living aboard, and have no problem sitting at anchor for 2 or 3 or 4 days waiting for suitable sailing winds, great.


But if you are like many of us, who like to sail, but occasionally need to motor home 30 miles, and really don't want to putter along at 3 knts, you may find that the battery is not up to it. Or if you find that you need to do two of those 30 mile days back to back (hey, the vacation ends on Monday and you are 60 miles from home), you are in trouble.


Or you start home and it's blowing 30 knts from the direction you are heading (my 34 monohull with a 27hp engine makes 3 knts with a wide open throttle in those conditions). Your choices are motor (figure out how big THAT battery needs to be!), sail (upwind in a Gemini in 30 knts?), or stay at anchor and call out of work Monday.

Just look really really really carefully at your use case, and then find someone who is living with it and loving it -- and have a few beers with them while talking about it. If you can find anyone who is actually using it for your use case.


Resale value is a concern too. If you decide you have no interest in motoring much, and you are OK with the limitations of electric -- it is good for you. The next buyer may want to motor down the ICW one year -- impossible on electric. Or want to cover ground on a week long cruise on the Chesapeake, where winds may or may not agree. He'll be looking at that electric and think "boat has no motor." But if you plan on keeping the boat 10 or 20 years, that's less of a concern.
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Old 06-12-2019, 12:03   #45
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Re: Gemini 105mc conversion Diesel to EV?

I wouldn't want to be stuck in the doldrums mid Atlantic in a Gemini. It all depends on what you want to use the boat for.

I converted a small runabout to electric recently, I've thought about converting a sailboat to electric.

Some advantages, ....

The electric motor is much smaller than the diesel it replaces, and 1/4 the weight.

Battery weight isn't as much an issue as you might think in a boat, and you can place them ANYWHERE you need a little ballast. (under the floor in a watertight box, near the actual keel is a great spot).

If you setup the system to regenerate, you can charge your bank while under sail.

A few solar panels will keep it topped off, (but unless you cover the boat with them, not enough to full charge).

System is very modular, and easy to work on.

For entering, and leaving the dock they work great, it is a sailboat, right?

Run out of gas? no problem, you can still run a reduced speed until the pack hits the low voltage cutout limit.

Quiet, and responsive, they really are more fun to drive.

Disadvantage, extended motoring at speed drains the pack frighteningly fast.

A car once it gets to speed the current draw drops off unless going uphill. A boat draws current linearly by speed.
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