**Diesel Engines**

**Hybrid Systems**

Parallel Propulsion

**What we like about a Parallel propulsion:
**

1) While motoring with the electric motors they are very quiet and don't smell.

2) Anytime we are motoring off batteries we are not burning diesel. That is around 3 to 5 hours of silent motoring each day. In fact, on 90% of passages we won't burn any diesel fuel at all if we have electric propulsion.

3) We will have more range than a Diesel or even the Hybrid boat, because you can motor off electric when you have the battery power, then switch to the more economic diesels (versus a generator), which gets rid of some of the conversion losses. (See the fuel comparison below).

4) Redundancy of two diesel engines.

**Combo Propulsion**

**What we like about a Combo propulsion system:
**

1) While motoring with the electric motors they are very quiet and don't smell.

2) Anytime we are motoring off batteries we are not burning diesel. That is around 2.6 to 4 hours of silent motoring each day (the range depends on if we are using our auxiliary battery as well). In fact, on 90% of passages we won't burn any diesel fuel at all if we have electric propulsion.

3) Our range is about the same as the Parallel system and we will have more range than a Diesel or Hybrid boat because we can motor off electric when we have the battery power then switch to the more economic diesel (versus a generator), which gets rid of some of the conversion losses. (See the fuel comparison below).

4) We will have more horsepower available than any of the other options because you may choose to power the boat from the diesel engine and one electric motor, simultaneously. This is excellent in a situation where more power is needed for a short time.

5) This system weighs less than all the others.

6) The larger 25kw electric motors will regenerate at a higher amount, offer more horse power than the parallel system, and recharge the batteries from our single diesel at more than the two 10kw motors of the parallel system running two diesels.

**PARALLEL SHAFT DRIVE**- Both the electric motors and diesel engines drive the same shaft and propeller.**REDUNDANT POWER**- If either the diesel or electric system has an issue, the other can still power the shaft.**RECHARGING**- While on diesel propulsion, the electric motors can charge the batteries.**REGENERATION**- While sailing, the prop can turn the electric motor, regenerating power to charge the batteries.**GENERATORS**- While at anchor, the engines can be used as 7 kw generators.**LIGHTER**- Because we are removing a generator and carrying less diesel fuel, the overall parallel system is much lighter than a diesel boat.

The Nanni N5.50 engines are 50hp each and come with Combi 10kw electric motors. The advantage of this system is that you have two diesel engines with a combined 100 hp or two 10kw electric motors. The disadvantage is that this will be heavier, cost more, regenerate less energy from sailing, have less electric propulsion at only 20 kw, total, of electric propulsion.

Stats Per Hull

Configuration - 4-stroke, vertical, water-cooled diesel

Max. output - 50 hp

Displacement - 2.19 ltr (134 cu in)

Cylinders - 4 in-line

Dry Weight - kg / 548 lbs

Combi 10kw electric motor (in parallel)

Max. output - 13.4 hp

Dry Weight - 341 kg / 150 pounds

As good as a Parallel system might be, our current choice for our new propulsion system is to go with one parallel diesel/electric engine/motor in one hull and one electric motor in the other hull (see image, right).

This Combo setup uses a Nanni 80hp Diesel engine with a Combi 25 kw electric motor in parallel, meaning they use the same drive shaft for propulsion. This will be in one hull while a Combi 25kw electric motor is in the opposite hull. We will store the batteries and dive compressor in the same hulls as the electric motor to offset the weight of the parallel diesel in the opposite hull.

The advantages of this system over the Parallel are far less cost, less weight, less fuel usage, less maintenance, and less money to install, yet this Combo system offers more horse power and better regeneration!

**PARALLEL SHAFT DRIVE**- In one hull, the electric motor and diesel engine both drive the same shaft and propeller.**REDUNDANT POWER**- If either the diesel or electric system has an issue, the other can still power the boat.**RECHARGING**- While on diesel propulsion, the 25kw electric motor can charge the batteries at up to a 14 kw maximum rate; we are figuring about 10 kw.**REGENERATION**- While sailing, the props can turn the two 25 kw electric motors, regenerating power to charge the batteries and again, at a higher rate than the Parallel's 10 kw motors. At 9 knots of boat speed, stats show this will be around 1 kw per motor!**GENERATOR**- While at anchor, the parallel diesel engine has a clutch to disengage the drive shaft. Therefore, the diesel can turn the 25kw electric motor and become a 12 kw generator.**LIGHTEST OF ALL**- Because we are removing a diesel engine and a separate generator while carrying less diesel fuel, the overall Combo system is 100s of pounds lighter than all other options.**Maintenance -**Also because we are removing two diesel engines from the boat, we will have less maintenance than any of the other propulsion systems.**Less Expensive**- It is less expensive than a Hybrid or Parallel system. Only Diesels are initially less, yet they will cost about the same over time due to fuel burn and maintenance savings.**HORSEPOWER**- These have an additional 23.5 hp over the parallel system!**BETTER FUEL MILEAGE**- the 80 hp diesel has about the same fuel mileage as a 45 hp diesel when they are both running on one diesel engine at the same horsepower for cruising speed. By comparing the power output vs rpm, and then how much fuel these engines burn a that rpm, if any of the diesels are pushing the boat at the same horsepower, the different size engines use nearly the same gallons per hour. However, the Combo system has a larger electric motor, so it will recharge our batteries faster. To get the same speed, we would have to run both diesels on the parallel system. Also, we can run the diesel as a lower RPM because the load is put on it by the Combi 25kw electric motor as it sends 12kw to the opposite hull Combi Electric Motor.

Stats Per Hull #1

Configuration - 4-stroke, vertical, water-cooled 4JH80 Yanmar diesel

Max. output - 80 hp

Displacement - 2. Liters (122 cu. in.)

Cylinders - 4 in-line

Combi 25 kw electric motor (in parallel)

Max. output - 33.5 hp

Dry Weight - kg / 568 pounds

Combi 25 kw Combi electric motor

Voltage: 48v

Max. output - equivalent of 33.5 hp

Dry Weight - 77 kg / 150 lbs.

Stats Per Hull #2

Configuration - 25 kw electric motor

Voltage: 48v

Max. output - equivalent of 33.5 hp

Dry Weight - 77 kg / 135 lbs.

Batteries: 22kw, 48v 200 kg / 440 lbs.

Aux Batteries: 11kw, 48v 220 lbs.

**Diesel Engines and Generator**- The two 55 hp diesels weigh 519 pounds, each. The 9 kw generator weighs 500 pounds. Being a diesel only boat, we would need to go with 150 gallons of diesel capacity. That much fuel weighs 1,050 pounds. House batteries (11 kWh) weigh 186 pounds.**Grand Total: 2,774 pounds.****Hybrid Motors and Generators**- The two OC SD15 motors weigh 42.5 pounds each. The two 20 kw diesel generators weigh 542.5 pounds each. The 44 kWh lithium battery bank plus the tender/auxiliary battery of 11.kWh, all total weighs 744 pounds. Typically, we would only need to carry 50% of our fuel capacity, so that weighs 350 pounds.**Grand Total: 2,264, or 2,614 pounds if we are full of diesel fuel for ocean crossings.****Parallel Engines with Motors**- The two 45 hp parallel engines weigh 548 pounds each. The two 10 kw motors weigh 90 pounds each. The 22 kWh main lithium batteries plus the tender/auxiliary battery of 11.kWh, all total, weigh 558 pounds. Typically, we only need to carry 50% of our fuel capacity, so that weighs 350 pounds.**Grand Total: 2,184, or 2,534 pounds if we are full of diesel fuel for ocean crossings.****Combo: Parallel Engine & Electric Motor**- The single 80 hp parallel engine weighs 568 pounds. The 25 kw parallel motor weighs 150 pounds (with brackets). The single 25 kw electric motor weighs 135 pounds. The 22 kWh main lithium batteries plus the tender/auxiliary battery of 11.kWh, all total, weighs 558 pounds. Typically, we only need to carry 50% of our fuel capacity, so that weighs 350 pounds.**Grand Total: 1,761, or 2,111 pounds if we are full of diesel fuel for ocean crossings.**

It is pretty simple, the Combo boats beats the Hybrid's 503 pounds. It beats the Parallel by 423 pounds. And it beats the Diesel boat by 1,013 or 663 even on ocean crossings!

The clear winner in weight is the Combo system as the lightest option. It is hundreds of pounds lighter than any of the others! And remember, keeping the weight down is absolutely critical on a performance catamaran!

When we compared all four of the propulsion types, using different length passages in different situations. We discovered that the Combo propulsion system is the obvious winner. This is simply because it has all the advantages of each system. It can function as a diesel boat, a hybrid boat, or a parallel boat, using whichever is the most fuel saving system at that moment. In fact, it pretty much ties or wins in every scenario we tested.

For Patrons, we offer detailed looks at everything we used in our comparisons as well as the results for each different passage calculated for each of the four propulsion systems. Just use this link or the button below to view the Fuel Comparison Data.

**Diesel Engines**- there are two 55 hp diesels Total: 110 hp**Hybrid motors**- There are two Oceanvolt 20kw electric motors, which supply about 30 hp each. Total: 60 hp**Parallel. 2 Engines & 2 Motors**- Two Combi 10 kw motors (13 hp ea., 26 total). Or two Yanmar 45hp diesels for a total of 90 hp.**Combo: Parallel Engine & Electric Motor**- One Combi 25 kw motor (33.5hp). Plus one Yanmar 80hp diesel with 25kw electric motor. Total (diesel plus the 25kw motor): 113.5 hp. Also, on only Combi electric motors we get 25kw + 25kw. That means she has 67 hp while using electric, which is 7 hp more than the hybrid boat.

As you can see, the Hybrid boat is woefully underpowered in comparison to the other three options. Horsepower is the category that eliminates the Hybrid from our consideration since that system does not have enough power to motor us out of a dire situation or get us up current while motoring on swiftly flowing river.

The Parallel system has 20 less horsepower than the Diesel.

However, the Combo system has a little more horse power than the Diesel boat, by 3.5 hp. That's not much, but we will take it.

So, of the three other systems, the Combo system boat has the most horsepower, slightly more than the diesel, and also slightly more electric propulsion horsepower than the hybrid.

Since it beats both diesel and electric horsepower, while having to push a boat that is hundreds of pounds lighter than the diesel, hybrid system, or parallel systems, the winner is the Combo system boat.

**Safety Consideration:**

Both the Diesel and Hybrid boat are not as safe as the Parallel or Combo boats which offer the total elimination of explosive fuels while having the required horsepower in certain situations. And, they both have redundant propulsion systems (electric and diesel).

The Combo system wins in every category we have listed: better fuel economy, more horsepower, less weight, added safety, and less cost in the long run. And, like the Hybrid and Parallel system boats, the Combo boat offers us all the comforts of electric propulsion with far less times than any of the other systems where we must obtain diesel fuel.

The reason it beats the others is simple. The Combo a can be a diesel boat, a hybrid boat, or a parallel boat, depending on which is best at that moment. And, it only has the weight and maintenance of one diesel engine.

Therefore, the Combo propulsion system is our winner, by a long shot. The initially cost will be around $12,000 more than the diesel boat, but worth it since the combo system should make up that money over time due to fuel savings while giving us all those other advantages.

That is why we decided that to go with with a Combo Hybrid Parallel Diesel system.

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