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Rules of Thumb


Diesel / Hybrid / Electric Drive

Why have one prop drive system, when you can have three?  This is what happens when you watch fuel prices and wonder how your going to pay for that stuff.

The current plan is to use a 150 to 200 hp diesel engine for full speed, an 25 kw (33 hp) 3 phase generator normally for shop power that can drive a 3 phase motor also connected to prop shaft and finally a 9 kw (12 hp) DC motor / generator that will be powered from the batteries and also recharge the batteries when under sail power.

Diesel Engine

Diesel Engine Tutorial

Growing up like most farm kids I worked my share of diesels in Case backhoes, Mercedes cars, International Harvester, and Ford tractors, but only replacing parts like starters, pumps and such. Until I got the Ford 7.3 for the submarine I had never messed with the fuel pump or glow plugs. You can read more about the Ford 7.3 here: Engine Tune Up

Having deciding to build a sail and charter work boat, I knew it was time to improve my skills. I did not want to be like the Captain of 20 years that we took our sailing course with and who had to call home when the engine would not start.

There are likely lots of good community college night courses on diesel mechanics, but I don't have the patience for spending my nights in a classroom, so I decided on a home study course and spent $3600 on truck with a 170 HP Caterpillar 3116 with 150,000 miles on it. It was the perfect comprehensive home diesel repair course. There was a chance that if we liked this engine it might be the engine we drop into the sailboat. At this point there that is not likely.  While you can get after market rebuild kits for the 3116, they just don't hold up like other engines. Which is one reason why you can buy a whole truck off a lot with one inside for $3600.  You can read more about our experiences with the Cat 3116 here: Tow Truck.

Boat Engine Requirements

Paul's boat is a 65 foot version of our boat and he is going to use a 50 Hp engine.  That is small for the size of boat but right for Paul's type of sailing. We on the other had plan to do charter work, salvage work and operate an ROV so we will sometimes need to get somewhere quickly and sometimes have the power to keep up out of trouble on a lee shore.  For us 170 Hp was likely too low to start with and now that our boat has grown to 70 feet, Jack, our designer is recommending something in the neighborhood of  200 to 250 Hp.

Whatever the HP, make, and model, the overriding requirement is that we need to be able to perform a complete overhaul using remanufactured parts without the block leaving the hull.  After that, the engine must be economical to operate and have parts widely available.

Engine Prospects

John Deere

Jack favors John Deere; www.deere.com, in part due to their use of sleeves for the cylinders that allow easy replacement if needed.  The John Deere PowerTech 6068 Marine Engine or 6068SFM is a 6 cyl, 6.8 liter, turbo charged, electronic fuel injected engine available in  154 Hp for continuous duty.

6068SFM Performance Data - 6.8 liter M1 M2
Rated Power--hp (kW) 154 (115) 236 (176)
Rated Speed--rpm 2300 2400
Low Idle Speed--rpm 650 650
Peak Torque--lb-ft (N.m) 741 (1005) 674 (914)
Peak Torque Speed--rpm 1600 1800
Fuel Consumption - gal/hr for specified rpm    
2400 N/A 9.2
2300 7.8 7.8
2200 6.7 6.8
2000 5.1 5.1
1800       (M2 Peek Torque) 3.7 3.8
1600       (M1 Peek Torque) 2.7 2.7

The same 6068SFM engine is for rated at various HP depending on how it will be used.  The only things that change is the higher HP engines flow more fuel and have a higher turbo boost setting.

The bottom line is that using lower HP will give you longer life and greater duty cycle. M1 ratings are 24 hour a day and 3,000 hours per year and M2 are for 16 hours a day. They also have M3 through M5 which would be good for a full-time sailboat, but since Seeker is for part-time charter work, then getting to a destination on time will sometimes be necessary.

The John Deere tractor series also uses the 6.8 liter engines. The 7430 is rate at 165 hp.  The intercoolers are air to air on tractors but most everything else should be the same. So there is a possibility of picking up a engine out of a tractor.

Other Potential John Deere Engines

4045  - 95 hp
3029T - 45 to 72 hp
4039D - 71 hp  (Rebuild kit is $720) 
  On a 60kw generator with 3500 hrs it cost $7,250 (ebay 2009)
  2000+ hrs engine only, wo/radiatior or muffler cost $1500 (craigslist 2009)
4024T - 43 hp
  On a Sullair 185 cfm compressor with 5600 hr is $3850 (craigslist 2009)
  On a Sullair 185 cfm compressor with 2600 hr is $2450 (Enlow Auction 2009)

John Deere 20 KW with and sits on 150 gallon double wall tank Stamford newage end with PMG, 500 hours $7,000 connect single or three phase.


The following Cummings models are in the correct power range:

Model HP RPM Peek
@ Peek
Fuel System Duty Cycle
QSB5.9-230 HD 225 2600 1600 3.1 Turbo Charged Heavy Duty
6CTA8.3-M 255 1800 1200 4.2 Turbo Charged Continuous
QSL9 - 285 CON 285 1800 1400 6.9 Turbo Charged Continuous





The Cummins C-Series has replaceable cylinder sleeves and 97 and older models use a very reliable mechanical injector according to a trusted diesel mechanic. The B-Series for 97 and older also have the mechanical injectors but not the replaceable wet sleeves. However even if you have the wet sleeves it may still be necessary to have the block pulled so the top of the block can be machined.  This can be done "in-frame" when the engine is in a truck, but not necessarily in a boat.

The Cummins 6C8.3-210 is 210 hp, with a maximum of 2400 rpm and peek torque of  446 lb-ft (605 Nm) at 1300 rpm. It was originally introduced in the late 1980s and co-designed with the Case Corporation.  It uses a very reliable mechanical injection, piston style fuel pump often called a "P-pump".

We almost purchased the bus in the video, but we did something smart.  This engine had sat for years, so we made the sale contingent on the bus making the 200 mile trip from Kansas to Tulsa.   It make it 100 miles before it blew up.  The coolant system was not working and it lost one cylinder at least.  So glad it was not me with a broken down bus on a Kansas roadway. 



Electric Drives

Need to Know

Watts = Amps * Volts {can also be written Power= current x voltage}
Amps = Watts / Volts
Volts = Watts / Amps
Watt-Hours = Volts * Amp-Hours {or energy = voltage x current x time}

Batteries in series = add voltages
Batteries in parallel = add amp-hours

Motors in series = divide voltage by # of motors
Motors in parallel = divide amps by # of motors

Power is measured in metric units as watts (W) or more commonly kilowatts (1kW=1000W) or horsepower in the imperial units (1hp = 746W).

Power (kW) =  Torque (Nm) x RPM / 9549
Power (hp) =  Torque (lb/ft) x RPM / 5252

Energy is what gives an electric car/boat range. It is the product of power or kW and time (E = P x t) or the product of voltage and amp-hours.  Kilowatt-Hours (kWh) stored in a battery is the measurement of total electrical energy.  For example a 12v, 55 amp hour battery at the 20 hour rate will provide; 12v x 55amp/hr = 660 watt-hours.   To power a 19.2 kW motor, we would need; 19,200 / 660 = 29 batteries.  But we can actually only about 10 actual before we have drained them to 55 or 60% which is their recommended depth of discharge.

Higher voltages = Higher motor RPM and higher top speed if we were powering a car, but powering a 40 ton boat to it's hull speed is not the goal and that propeller is sized for lots of torque and only about 600 rpm so we will be gearing the motor down even with lower voltages. Higher voltages are often more efficient, and if we had 120v DC, then many of the shop tools could be powered directly from the battery, so it's worth keeping in mind.

Power Requirements

Power Recommendation from Emotion Hybrids site electricmarinepropulsion.org :

Emotion Hybrids site electricmarinepropulsion.org
Power output
Max, current draw
Max. prop diameter*
Max. displacement
Max. monohull length**
16 kw
120 lb-ft (160 N-m)
144 vdc
111 amps
130 lb (59 kg)
19 in (483 mm)
11 in (279 mm)
25 in (635 mm)
26 t (23.6 mt)
50 ft (15.2 m)

Emotion Hybrids recommends a 120 lb-ft motor for 26 tons, so Seeker with 40 tons would need about 200 lb-ft torque. Compare that to a John Deer 6068 with 741 lb-ft at 1800 rpm and it's easy to see that it's certainly less power.  The 6068 will loose a lot of torque to the transmission but I doubt it comes anywhere near 541 lb-ft.

If we decided that 300 lb/ft is sufficient then we can get that from a 100HP DC motor. A 100HP Motor at 1750 rpm = 300 lb/ft torque:
T = HP x 5252 / rpm   =  100 x 5252 / 1750  =  300 lb/ft

Bigger DC Motors do exist: Horsepower 100, RPM 1750/2000, Weight 1118 lbs, Cost $13,777.  Plus; Variable Speed DC Motor Drive, Input 230VAC Three Phase, Output 240VDC Armature, 100 HP, 330 Amps Cost $4,952.  That is 330 a x 230 v = 75.9 kw and is in line with the 115 kw from a John Deer 6068 M1.

www.driveswarehouse.com   The cost is considerable because this is just the motor and not the generator/s.  Used units with controllers are available for 25% of the new cost but these motors are not specifically designed for regenerative prop drive so they are not going to be as efficient or practical. A 35kw, 3 phase Onan diesel generator used will cost around $7000.  The up side of this approach is that the boat's shop will need lots of electric power and so having a big generator would be nice.

Ton Displacement / Kilo Watt





Maximum Recommended
Displacement in tons
Claimed Diesel Equivalent in HP Ratio
www.solidnav.com Explorer  4 5.3 6 24 1.5
electricmarinepropulsion.org E motion 16 21.5 26   1.6
www.asmomarine.com   17 22.8   52 to 60  




Based on these vendors standards, Seeker at 40 ton would need a 27 kw motor and unloaded at 20 tons would need 13 kw.  Because we only intend the motor for slow speed then perhaps 10kw will suffice.  Besides motor will need to be adjusted according to the cost and size of the battery as well as the ability for us to recharge it using solar, wind, and prop.

DC Motors

Thoosa 17000 from Asmo Marine, www.asmomarine.com and also www.ngcmarine.com is a 96V, 200 amp, 17kW said to replace a 52HP-60HP engine. These use a cog belt reduction to the drive shaft.  The motor works as a generator and charges the battery bank, while the boat is driven by sails or engine in excess of the motor's throttle speed. 

Advanced DC #L91-4003  72-120 volt, reversible motor from www.evparts.com
Current Ratings: 130 amps continuous, 150 amps for one hour, 500 amps peak
Horsepower Ratings:  At 96 VDC, 13.6 HP continuous, 15 HP for one hour, 26.4 for 5 min., 62 HP peak
At 120 VDC, 16 HP continuous, 17.9 HP for one hour, 31 HP for five min., 72 HP peak
One Hour KW rating: 11.4KW @ 96VDC, 13.5KW @ 120VDC
Weight: 85 pounds

Others: http://www.hydrogenappliances.com/manta.html

A good idea from Richard Clifford-Smith:  How well the permanent magnet motors work as generators depends on how fast the prop can spin them when you are under sail. If that was a problem they could perhaps be connected in parallel for driving the prop but series for charging when sailing. Failing that it is possible to convert dc voltages both up and down using electronics.

AC Motors

Most big industrial motors are AC. And 3 phase AC motors are sometimes used on eclectic vehicles, especially the larger EV's like buses. They lack the same high torque at low rpm as the DC motors but they are slightly more efficient.  A 3 phase AC motor will require a revising motor starter with an overload relay. Even better would be a variable frequency speed controller.  When using the AC motor to maneuver it will be necessary to repeatedly turn it on and off and possibly reverse the direction.  If a smaller DC motor is available this job could be left to it, but if the AC motor is doing the work then it starting surge would quickly over heat it. Using a frequency speed controller would allow it to run a slow speeds instead of being turn off, and when the direction is reversed it would ramp the speed down, reverse the motor and ramp the speed back up.


Just for a starting point, we'll work with a 48 volt forklift motor running at 10 kw or 208 amps.  If we want to run this motor at this power for 6 hours, then we will consume; 10 kw x 6 hrs = 60 kWh (kilowatt hours).  The useable amp hour storage for the battery is; 60 kWh / 48 v = 1250 amp hours.   The usable amp hours supplied by a battery are 1/2 the advertised amp hours if the battery allows a 50% depth of discharge.  So in reality to get 1250 amp hours from batteries with a maximum recommended depth of discharge (DOD) of 50% we nee two 1250 amp hour batteries or a total of 120 kWh.

For example Solar One has batteries with a DOD or 80%, but only taking them down to 50% will guarantee a longer life. However their 1270 amp hour batteries are $12,620 each.  $26,000 for two batteries.  Wow!  That's the price of a new 200 HP marine engine. These batteries should be able to provided 1250 amp hours 2500 times before they need to be replaced.  So that is 2500 x 6 hrs = 15,000 hours of electric motoring.  My guess is that if you got 15,000 hour out of a marine diesel that you would feel good about it.  However a 10 kw (13 HP) diesel is only going to cost about $2000 but it drinks about .4 gallons per hour.  That comes to 15,000 hours x .4 gph = 6000 gallons of fuel.  At lets say $4.5 per gallon, that is 4.5 x 6000 = $27,000 of fuel.  I doubt many $2000 diesels will live 15,000 hours either, but we still have the cost of solar panels and wind and prop chargers to put 60 kWh back into the batteries.

6 - 1000 kw solar panels provide 6 kw for 6 hours a day = 36 kWh.  They also cost about $1000 each. With losses, we will need 2 days of sitting in the sun for every 6 hours of electric motoring.

An amp hour (AH) is a rating usually found on deep cycle batteries. If a battery is rated at 100 amp hours it should deliver 5 amps for 20 hours, 20 amps for 5 hours, etc.

With a 200 amp draw at full power, it would be best to have a battery bank that would provide 200 amps per hour at 96 volts over 20 hours and only discharge the batteries to 50% which is the maximum "depth of discharge" recommended for lead acid batteries and well above the 80% DOD allowed for some deep cycle batteries.  Allowing for a constant 200 amp load without damaging the battery bank.  A typical 12 volt, AGM, is 55 amp hour, so 4 of then would provide 220 amp hours at 12 volt, and 8 times 12 makes the required 96 volts, so that comes to 32 batteries.  At $165 each that comes to just under $5280 for the batteries.

A commercially-available deep-cycle battery storing a nominal 1.2 kWh costs approximately $70 US at retail. The AGM's listed above are 12v x 55 amp hour = 660 watt-hours or about $330 for 1.2 kWh. 

In kWh or kilowatt hours, the same 200 amp motor at 96 volts is using 19.2 kilowatts ( 200 x 96 = 19,200 ).  19.2 kW * 1 hours of run time = 19.2 kWh.  19.2 kWh / 660 Watt-Hr per 1 AGM = 29 Batteries for 1 Hour

The upside to a lot of batteries is that they can be hooked up to a rectifier in order to supply AC power to the shop tools, and it provides a large capacity for storing power generated by solar panels, prop and wind. At 43 pounds each it is also 1000 pounds of ballast.  They are 10 1/2" x 7 3/8" x 8 3/4" so it would be easy to put all of then in the top of one of the keels. Having 96 volt DC available also makes it possible to run some of the tools directly from a 96 volt DC motor.

Off-grid homes that uses there batteries for large house loads are a better model for how we plan to use our batteries than are most marine power applications. With that in mind Trojan: www.trojan-battery.com, T-105s or L16s are popular choices that provide over 1500 cycles to 35 percent discharged.  However HUP Solar One batteries; www.hupsolarone.com, manufactured by General Battery, are considerably more robust. These are warranted to endure 2,100 cycles of 80-percent discharge, or 4,000 cycles of 50-percent discharge.  These are also massive batteries that will require a crane to move.

An off-grid formula from Solar One is: (Daily Power Consumption kWh) X (Days of Autonomy) X (1.2 80%DOD) x (1.3 System Losses) = Battery capacity. Our 10 kW Motor x 12 hours x 1.2 x 1.3 = 187 Usable kWh.  This would require 3 - Solar One, SO-6-85-33, 48v 64.8 kWh at 20 hour rate batteries which are 5344/lb each for a total of 8 tons. But the real problem is that the total cost is $15,600 for a total cost of $46,800.  So we need a smaller motor or a shorter run time because $15,600 is about the limit of our budget.


Calculate Solar Watts Available http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/

Motors Controllers

"For many applications including heavier vehicles and heavy boats an electronic controller is necessary. For boats and low-speed vehicles (below 15 to 20 Km/h, 9 to 12 mph) we recommend those made by 4QD, the Curtis 1225 and 1227, the Sevcon Millipak 4QPM (all of which give forward, reverse and regenerative braking) and the Curtis 1204, 1205 and 1209 (single direction but can reverse or brake by use of switch or contactor; 12 volt versions of the 1204 and 1205 are available on request but are not listed in Curtisís catalogue). The Curtis 1225/1227 and Sevcon are microprocessor-controlled and if you wish to alter their settings you need either a programmer or an adaptor and software to connect them to a personal computer."
-- www.agnimotors.com


DC generators are more expensive than AC generators.  A DC generator can feeding through a high voltage battery pack. An AC generator would need to feed a battery charger, but it could also feed 3 phase AC power to an AC motor.  The shop and tools on board need AC and having 3 phase for the compressor and plasma cutter would be ideal.  DC generators start off by generation AC and then rectifying it with diodes, so an AC generator may be the best path.  Then a rectifier could be added to power a DC motor.

A 50kW diesel generator that says it uses 4.2 gallons per hour at full load, 3.3 gph at 3/4 load, 2.4 gph at 1/2 load, and 1.8 gph at 1/4 load. Full load for an hour would be 50 kWh, so that would be 4.2/50 or .084 gallons per kWh. If diesel is $4.50 per gallon, that would be about $0.38 per kWh. If you run at 1/4 load, 12.5 kW instead of 50 Kw, you would pay $0.65 per kWh.

So the generator needs to be sized for the shop loads and the electric motor needs to be sized for the same load so that the generator can always run at full load.

Fuel Efficiency and Cost Variations Example
#1  www.jobsite-generators.com 20 kW (25 kVA) Ultra Silent Diesel Generator - Multiquip $17,000
1.44 gph;  Cost per kwh = 1.44 x $4.5gal / 20 = .324 cents
#2 www.harborfreight.com Reconditioned 20 KW Generator, Detroit Diesel $4,300
2.40 gph;  Cost per kwh = 2.4 x $4.5gal / 20 = .54 cents

The #2 generator saves $12,300 off the purchase price.  If diesel is $5/gal is cost $4.80 more an hour to run, so it will cost the same as the #1 generator after 2,562 hours. 

#3 www.ebay.com Kubota Quietrun housed 3,500 Watt Diesel Generator -- $6,850
.94 gph;  Cost per kwh = .94 x $4.5gal / 3.5kw  = 1.20 cents

#3 Shows that bigger is better! Bigger generators are more efficient.

#4 www.ebay.com Kubota 21 kw, open frame -- $7850
2 gph;  Cost per kwh = 2 x $4.5gal / 21kw  = .43 cents


Hybrid Electric Drive Installation Example

1968 Owens Yacht
42' Hybrid Electric Baldor Compound Wound DC
12HP, 72 Volt, 15" Prop , Contactor reversing
4 Trojan 360AH, 6.00 Volt, Lead-Acid, Flooded
4 360AH in series for 24 Volt
8 Knots (5 MPH)
Range: 3 Miles

First, I had twin Chrysler 440's gas engines.
I cut a sprocket in half and drilled some holes in one half and threaded the other half.
Put the sprocket around the prop shaft a few inches back of the transmission.
I used a compound wound motor so it would charge when the gas engine was turning the motor. I could take the chain off when I did not want to turn the electric motor.
I geared down with belts on one end of a jack shaft I put where the motor was mounted back to the prop shaft. --Jack.

Another Example

"In the last issue of the DBA (used to be Dutch Barge Association) newsletter there was an article by a guy who had remotorised his barge by chucking out a 5litre diesel and installing 4 10kw pancake DC motors instead. Batteries were charged either from shore or from a 13kw generator, which I assume would be on a good bit of the time, particularly when maximum power was needed when it would augment the battery. The rig was pretty expensive - about £23k from memory - but he did give some power consumption figures. As usual with a displacement hull - 50ft long in this case - they just went to demonstrate that piling in the power doesn't increase the speed all that much, but the interesting bit was that you could get about 4knots with under 5hp and this is the sort of speed limit you are stuck with on a lot of inland waterways. However he thought that it was turning out more economical than a straight diesel - particularly if you can get your batteries charged up at a marina. My thought was that it would be better to have 2 of these motors, one of which could be a backup/run as a generator, and keep a medium sized diesel in reserve for when you need the extra power for punching up a river or against a tide. Otherwise use a low powered and quiet electrical rig - unless you have a sailing barge and the wind is right."  --Andy Airey


Jack's recommendation is a transmission from Twin Disc; www.twindisc.com.  The Twin Disc MG-5061, SC straight shaft or A for 10 degree down shaft comes in a 3:1 reduction rated for continuous duty with 170 hp @ 2100 rpm.  And it retails for $5,500 in 2010. The 5050 retails for $4,500 but with 3:1 reduction it is only continuous duty rated for 145 hp @ 2100 rpm continuous duty. They come SAE 2 or 3 bell housing and a torsion coupler that fits either the 11 1/2" or 14" flywheel.  One of the down sides to a twin disk transmission as with most marine transmissions on sailboats is wind milling. When the transmission is in neutral while under sail power, the water flowing past the prop will cause it to turn the shaft as well as the gears in the transmission.  This is fine for about 8 hours with Twin Disc transmissions but after that long the engine needs to be started so oil is pumped to the bearings. The alternative is to lock the drive shaft so it can not turn.  In our case, we want to be able to use the wind milling shaft to turn a small DC generator to resupply the battery storage. In this case, even the friction from the gears in the transmission is undesirable.  So our solution will be to install a drive line disconnect, which is a simple a dog clutch that separates the propeller shaft from the transmission.  See: Propeller Shaft Disconnect below.

There is an excellent book called Marine Conversions by Nigel Warren.  It's old and out of print but well worth having your local library find it through the inter-library loan program.  Or Click here to check for a library near you.  It shows several conversions that can be done for automotive engines and transmissions. 

Thrust Bearing

Aquadrive Thrust Bearing & CV
joint drive shaft.

The force from  the prop is best applied to the hull through a thrust bearing just in front of the stuffing box.  This allows for the use of U-joints in the propeller shaft and for the engine and transmission to rest of soft mounts that absorb the vibrations.  The down side is that off-the-shelf thrust bearings are expensive.

Aquadrive sells a thrust bearing and CV joint drive shaft, but the CVB 42.30 model we would need cost just under $6000.  That seems a bit steep considering a brand new Twin Disc transmission for us would be the same price.

An alternative might be just good old thrust bearings from the front wheels of a big truck or bus. We already plan to use the propeller shafts from a bus for the dive shaft from the thrust bearing to the transmission.

210 hp @ 2400 rpm through a 3:1 transmission is 800 rpm, 1319 lbft on the shaft, and 3702 lbf of thrust.

Propeller Shaft Disconnect

Trail Tough Driveline Disconnect

Remco Dive Shaft Coupling

Trail Tough makes a driveline disconnect for $429 (2010) I talked to Brent at Trail Tough and while than have no tested torque values, he says our 1320lbft torque is "nothing".  "These are on rock crawlers with 500 hp engines."  And he says they have only seen 1 failure and that was due to heat.  The down side to this design is that it is built to fit the transfer case on a Suzuki or Toyota mini-truck transfer case.  We would have to adapt it to our transmission. It must be under no load to engage or disengage, but it only needs to turn a few degrees before the splines can lineup.

A Remco Drive Shaft Coupling is another option for just under $1000 (2010).  I talked to Jason who is an engineer at Super Flow, the parent company of Remco and the unit can  take of 2200 ftlb torque which should be fine for our application as we don't have any high shock loads.  The upside of the Remco design is that they fit between the U-Joint coming off the transfer case so it might be easier to adapt.  Especially if we use a road transmission and not a marine transmission.

Thrust Bearing Block

2" Thrust Bearing Block  $180







Thrust Bearing and Drive Shaft Disconnect

Dana 30 - Front Outer Bearing

An axle off a 4 wheel drive that uses a Center Axle Disconnect can serve as the thrust bearing and a dive shaft disconnect. A Dana Model 30 Front Axle 1987-1995 Jeep Wrangler YJ  for example has conical front wheel bearing is designed to take thrust as well as load, and there is a vacuum motor on the axel tube which operates a dog clutch to disconnect the two piece axel between the hub and the differential.  For a smaller engine the Dana 30 would likely do well, but I'm worried about putting 440 lb-ft from a Cummins 5.9 diesel through the 1 1/4 inch axle even if it is hardened steel and supports torque numbers up to 2,500 ft-lbs. 

I think bigger is better and a Dana 60 has 1.5" front axels with 35 splines; more splines is stronger.  From 94 to 02, Dodge Dana 60 axles utilized a Center Axle Disconnect (CAD) system.  The splined collar is normally moved by a vacuum motor but that can be replace by cable system called a Posi-Lock for about $200, but a DIY Posi-Lock is not complicated.

Dana 60 Front Axle with Center Axle Disconnect (CAD)

DIY Posi-Lock - Cable
replacement for vacuum motor


The splined collar is normally moved by a vacuum motor but that can be replace by cable system called a Posi-Lock for about $200, but a DIY Posi-Lock is not complicated.










PTO Slip Clutch

Normally these are used on implements such as mowers running off a farm tractor's PTO, but I think rocks and logs in the water are not much different that rocks and logs in a field so I've decided to all one of these to my propeller shaft just behind the thrust bearing.  Smaller units like this 1 3/8" smooth shaft cost about $130, but the are designed for 65 Hp and not the 200 Hp of our Cummins.





Just an Idea

For starters we found 14 windows for our pilot house and drove them home for $500. They even came with their very own running school bus which is going to provided lots of others parts as well as it's windows. But we've been looking electric drives still and that bus differential got me thinking about the following. I know its not KISS but it's not the first time I've been Stupid and I rather enjoy the creative mixes of technologies even if it is more work.

On a 40 ton displacement boat, there is just no-way I'm going to replace a big turbo charged diesel with an electric motor. The number of generators and power combiner box, frequency speed control, and huge AC motor is just too much for me to deal with. So the big turbo charged diesel stays. However we still plan on having a lot of power hungry tools in the hold so we need a 20 wk, 3 phase, diesel generator as well as a large bank of batteries to power moderate loads without the generator and to store free power from sun, wind, and prop regeneration.

That 20 kw generator will burn about 1.4 gph at full load. Just starting the John Deer 6068  up means we start burning 2.7+ gph and it goes up to about 9 or 10 gph. So to me it makes sense to consider adding a 20 kw 3 phase AC motor that can be used for slow speeds and powered off that generator. This also provides a backup propulsion system should the main engine need repairs. The problem is the losses between the engine and generator and motor.  It would not likely save much using low cost equipment anyway.

A 10 to 17 kw permanent magnet DC motor could be powered off the DC battery bank for making short hops. The DC motor on the drive shaft would also provide a method for regenerating off the prop when under sail or when under generator or diesel power.  AgniMotors; www.agnimotors.com, makes high efficiency motors in the 10 kw range that sell for around $1,100 (2009). Now there is a Chinese version: http://www.hydrogenappliances.com/manta.html

While standing beside our school bus today I decided that the rear end differential might be a good way to put both a big diesel and the/or AC and/or DC motors onto the drive shaft and save buying a real gearbox. The diesel could be set in transverse to prop shaft and off to one side and connect to the differential through a drive shaft directly from the flywheel. The differential would provide something close to a 4:1 gear reduction as it normally would. One axle would connect to the prop shaft and the other would connect to the electric motors. This axle would also have a shaft break. With the break applied on the AC/DC motor axle the diesel would spin the prop. When the diesel is shutdown either the AC or DC motor or both could be engaged with a clutch and belt or with a spur gear that slides into place onto a keyway in the axle. The break would be released and the prop would either be power by the AC or DC or both motors, or it could spin the DC motor to regenerate and charge the batteries. The compression in the diesel and the gear reduction would prevent that drive shaft from turning when the electric motors are spinning. Docking, which we will seldom do will be done under AC or DC power because that is the only way we have reverse available.

Oh; No we are not tree huggers. If we though diesel was going to be $3 a gallon, we would not even consider electric drive :)

Mekanord makes marine transmissions for twin engines on a single drive shaft.  www.mekanord.dk/?id=83

(1) Patten using a custom
differential gear box.

(2) School Bus - purchased for
$500 for it's windows.

(3) Axle removed from rear end.

(4) Removed the bearing
retainer nuts.  


(5) Rotor and wheel hub

(6) Salvaged propeller shaft.
(7) The drive shaft connect to
the spur gear that is facing up
in these photos.  The spur gear
meshes with the beveled teeth
of the larger ring gear. The
cylinder bolted to the ring gear
contains the 4 beveled spider
gears. The axles are fit into
spines in the center of 2 of the
spider gears.

I did fine an example amongst patents for a boat drive that uses a custom differential gear. This idea was really furthered along after we purchased an old school bus.  We really wanted the windows for the pilot house but it turns out that it has an Eaton differential with a 3.25/1 gear when you lock up one axel.  That will be perfect for turning a big 33 inch diameter, 27 (40 ton) to 29 (20 ton) inch pitch propeller efficiently.

(3) The axle was not easy to remove due to a slew of bolts holding it in place. The outside of each axle is welded to a round steel plate that bolts to the wheel and rotor assembly.  That assembly rides on the outside of the axle tube using two large sets of roller bearings.

(4) Next the outside bearing retainer nuts are removed. They are not very tight, and good thing too because I do not have a socket in the neighborhood of 4 inches.  A hammer and big screwdriver did the trick.  (5) Once the retainer nuts are off the 100 pounds of rotor and wheel hub can be removed, and then the rotor shield and brake mounting bracket come off.

(6) If we abandon the idea of getting a used variable pitch prop, then there is no reason why we can't deliver the rotation force to the prop with the drive shaft also salvaged from the bus. There is 1-3' and 3-4' sections.  I think it's interesting and now fitting that my large truck repair manual actually calls the trucks drive shaft an "propeller shaft".  Proof that man ascended from the waters.

After some research on differentials I've learned that I need an "open differential".  This type will allow all of the power to go to one axle without any attempt to provide tork to the other axle.  Really bad for driving on mud or ice, but perfect for my needs. When I turn one axle by hand the other axle turns in the opposite direction so it should be a standard, open differential.

The pinion, ring, and spider gears all come out of the rear end housing as a complete unit.  There was no need to remove the drive shaft yoke or bearing from the pinion gear shaft before removing the unit from the housing.  The gear unit must weigh close to 150 pounds and with it removed, it will be much easier to modify the axle housing.

The big question in this plan is weather the


The modifications without the variable pitch prop control gear will only be to cut away most of the wheel from the prop shaft side and weld on a shaft yoke to the end of the axle. The other end will have a drive pulley mounted onto it that will be driven by a motor that is mounted to the axle tube. If a CPP is used then I may need to cut down one of the axle tubes and fit it with custom bearings in order to make from for the prop control box.

The rear end is an Eaton #303776 Model: 19050S, Serial # S0619 222. 







Electric Drive Example


Electric Drive Links

www.electricyacht.com  Only smaller units.
www.solidnav.com Only smaller units. 4kw, 6 ton
asmomarine.com ASMO Marine - DC Motors with regenerative controllers.
electricmarinepropulsion.org  Emotion Hybrids - DC Motors with regenerative controllers.
glacierbay.com  Marine DC motors, 20 hp - 800 hp, OSSA Powerlite www.ossapowerlite.com
abovethewaterline.net  DC generators, solar panels, etc.
re-e-power.com  Big trolling motors
fischerpanda.com  AC and DC generators, DC is more efficient but more expensive too.
solomontechnologies.com  for boats displacing up to 10 tons 16+ tons
polarpowerinc.com  Web site sucks

EV Links



www.lmcltd.net Lynch Motor Company
www.agnimotors.com Agni Motors

DIY Motor/Generator


EV Suppliers

www.metricmind.com  --AC Motors, Controllers, and Inverters
www.kellycontroller.com  --Sell 4Q Regen Controller but it is 120A, 72V, 8.6Kw
www.agnimotors.com -- Next generation Lynch motor

DC Motor Clutch

Mechanical: http://members.aol.com/pullingtractor/clutch.htm

Rules of Thumb

A kilowatt is approximately equivalent to 1.34 horsepower.  So 141.74 KW * 1.34 =  189.93 HP



New and Used Engines