Jimmy Cornell goes Electric, with a Cat

[sailingharry]

Well, that's a phenomenal amount of research, internalizing, and sharing! Yes, good stuff. It generally reaffirms my thought that the "heat" was a big driver, although your data scales back my thoughts some.


I did somewhat overstate the 1000 times, and I also somewhat didn't know the data. I did realize that I was rounding up. I was assuming an inductive burner was over 1KW, so I should have written more like 700. I actually think I was SWAG-ing 1W and 1KW, but you are right that those are not really appropriate. Guilty as charged!


I'm looking to upgrade my solar (4 flexible 10 year old 90W units), I could replace the two on the arch with with a pair of 240W units -- but the aesthetic police won't let me.... LOL. Probably end up with a pair of 180W units, still a huge increase.


The small induction hob is really tempting. Cheap, easy to store, no installation, low power when on battery and no power when plugged in.



My inverter is 1KW. Modified Sine. Ca 1998. ARGH! But how do I replace something that meets 100% of my current needs? LOL I keep thinking that an upgrade to a 2KW pure sine would be so sweet....and then I ask, just WHY? My current AC needs are the microwave (I understand that takes a hit on output power), the drip coffee maker, the laptop charger, and the cordless tool charger. Oh, and a little Dirt Devil Vacuum. Not very A/C dependent!

[Adelie]

Originally Posted by sailingharry

Well, that's a phenomenal amount of research, internalizing, and sharing! Yes, good stuff. It generally reaffirms my thought that the "heat" was a big driver, although your data scales back my thoughts some.


I did somewhat overstate the 1000 times, and I also somewhat didn't know the data. I did realize that I was rounding up. I was assuming an inductive burner was over 1KW, so I should have written more like 700. I actually think I was SWAG-ing 1W and 1KW, but you are right that those are not really appropriate. Guilty as charged!


I'm looking to upgrade my solar (4 flexible 10 year old 90W units), I could replace the two on the arch with with a pair of 240W units -- but the aesthetic police won't let me.... LOL. Probably end up with a pair of 180W units, still a huge increase.


The small induction hob is really tempting. Cheap, easy to store, no installation, low power when on battery and no power when plugged in.



My inverter is 1KW. Modified Sine. Ca 1998. ARGH! But how do I replace something that meets 100% of my current needs? LOL I keep thinking that an upgrade to a 2KW pure sine would be so sweet....and then I ask, just WHY? My current AC needs are the microwave (I understand that takes a hit on output power), the drip coffee maker, the laptop charger, and the cordless tool charger. Oh, and a little Dirt Devil Vacuum. Not very A/C dependent!

From my research, you need a better wave than a Modified sine to run an induction hob. Some may work with a ModWave but many won't or will be damaged.

The microwave is only 46% efficient. I tested it at the same time I tested butane vs induction.

Actually for heating water, I believe a little electric kettle is the most efficient, over 90% but I haven't tested that myself so I can't say for sure. The electric kettle loses less heat the environment, the only loss of efficiency is heating up the material of the kettle itself. If I was going to go this route I would get a fat separating measuring cup so that I could accurately measure water into the kettle and the long spout of the cup means I don't need a funnel.
https://www.target.com/p/oxo-2-cup-f...E&gclsrc=aw.ds

Research for this was an interesting challenge and I was sick of folks arguing back and forth about what could or couldn't be done with just gut feelings or anecdotal evidence to go on.

I won't say there aren't issues that need to be taken into account with an electric galley, but

As I stated I haven't tested ovens yet and I need to buy a convection oven for this and to borrow somebody's propane oven for comparison.
The hard part is figuring out what to test in the oven.
-I'm thinking a batch of Tollhouse cookies done as a single bar (like brownies) but deciding when they are done has always been a by eye thing for me so doneness is a bit subjective.
-I want to do chickens too. Get matching chickens exactly the same weight. Maybe put a thermometers in both breasts of each chicken and say they are done when the average of the two reaches a certain temp (165F). That will probably be better than the cookies, less subjective determination of end of test.
-I'm thinking maybe a jug of water in a metal container. Very easy to get both samples exactly the same for the start of the test but the water will be subject to convection and no food that you would bake is like that.
-I want to do loaves of bread so that I can compare propane, convection and breadmaker. I bet the bread maker wins with the light machine that easily comes to temp and the tight casing with low heat loss to the environment which probably will overcome the extra energy it uses to mix the dough and still be ahead of the convection oven.

I'm open to suggestions about what else I can try baking. The key thing is it needs to be something moderately heavy and with an easily defined point at which you can say it's done.


I found the post I did for testing butane vs induction and an equivalency chart for predicting electrical use based on current propane consumption.
https://www.cruisersforum.com/forums...ml#post3157825
https://www.cruisersforum.com/forums...ml#post3157686

[valhalla360]

Originally Posted by sailingharry

Plugging in isn't as easy as it sounds. I just did some math. Assume you want to motor with 10HP for 5 hours, and then recharge at a dock. That's 35KWh (10HPx700W/HPx5h). A typical 30A shore power cable is good for around 3KW. That's 10 hours at 100% circuit capacity to recharge! Frankly, I wouldn't want to see that load put on a typical marina circuit for that long.


Let's not even think about cost! 10HP for 5 hours is probably around 3 gallons of fuel, or $10 here in the US. Shore power connection is $15/night, but I've seen more.

I only did this math for a moderate motor for single day. I suspect Jimmy's bank can support at least this much, and hopefully much more (so even longer to recharge). I didn't consider 50A cables (are they 220V? That would be a big improvement!). I didn't consider house loads, etc. Just a single discharge and recharge cycle. You often hear "just plug in" but I've never considered (or run the math) on the impact of that.

Actually, for a use case where you are making 5hr marina hops, it's not nearly as bad as you make it out to be. If you are motoring for 5hr and tied up at dock for 19hr, you only need to pull 1.8kw to replace the 35kwh. That leaves plenty of headroom for moderate house loads even including a medium size air/con unit.

Of course, that's assuming a 30amp/120v shorepower. If you go with a 50amp/240v shorepower, you could pull 10kw continuous staying well below the 12kw peak allowable. That would recharge 35kwh in about 3.5hr.

Now if you are going into a marina specifically to get power, then of course, it will be expensive but for many coastal cruisers, it's common to stop at a marina for the evening, so that cost is present with or without battery electric drive. Worst case they charge you the kwh rate which will likely be $3-4. I'm not sure what boat you are spec'ing but 5hr at 10hp engine output, 3 gallons is quite good...I would expect most boats would be up around 4-5gal...so $12-15 (assuming $3/gal).

Of course, fuel savings alone won't justify a repower but a simple system with a coastal cruising focus will cost little if anything more (the Cornell boat appears to be an expensive boondogle). The biggest issue is finding the use case that works and coastal cruising as a Plug-In-Hybrid is pretty viable if you run the numbers.

[sailingharry]

Originally Posted by valhalla360

I'm not sure what boat you are spec'ing but 5hr at 10hp engine output, 3 gallons is quite good...I would expect most boats would be up around 4-5gal...so $12-15 (assuming $3/gal).

It was a hypothetical use case, but I was trying to be low, not high.


My Sabre 34, with a 23HP Volvo (underpowered) was normally run at close to WOT just to get decent speeds (near 6kts). It used .5 GPH, so 5 hours was 2.5 Gal and I'm pretty sure I was using mid-teens HP.


My Saga 43, with a 55HP Yanmar, is normally run at about 80% RPMs. Not sure what HP I'm drawing, but it has to be in the 30 HP range at least. It burns almost exactly 1 GPH (actually, closer to .95 or so, which makes mental arithmetic be slightly conservative).


Backing down the higher horsepower fairly significantly on the Yanmar, and using the Volvo straight up, tells me that using 10HP should really run around .5GPH. I fudged that up to .66, just to be generous.


I also pushed the HP down, as the EP folks are huge proponents of not pushing the boat -- the 7+ kts I usually motor on my Saga are not at all in line with the EP use case, they normally discuss 3, 4, or maybe 5 kts. I didn't want to come up with stupid high numbers just to prove *MY* point -- I wanted realistic numbers.

[mglonnro]

I think the best way to make the equation work:

- Forget about motoring for long stretches, it's primarily a sailboat with supplementary propulsion to be used sparsely and temporarily.
- Plug in whenever possible (it's not that expensive over here, usually 5-7 eur/24h).
- Optimize electricity usage to match solar and prop regeneration.

Heating, I don't know.

OV offers between 10-40 nm "pure electric" ranges for different models over here: https://oceanvolt.com/standard-systems/

[seandepagnier]

Originally Posted by fxykty

Watt & Sea figured out a variable prop that auto adjusts for speeds up to 25 knots. That’s a system that works! OV in auto mode doesn’t, and in manual mode who knows?

variable propeller aside, it's strange that OV doesn't have an MPPT algorithm for regen. This is not a very complicated control loop to write, I have implemented it on my solar chargers... I have prototype wind and hydro turbine controllers i'm going to test soon.


It is also strange that OV doesn't offer options for optimum propulsion, regeneration as well as a compromise turbine (which is less terrible at regeneration, but able to work as a propeller when needed but less efficiently) rather than using a standard propeller in every case.

Originally Posted by Adelie

SH:
What are the big energy users on a very comfortably outfitted yacht:
Propulsion

The issue here is to be "comfortable" is really a disguise for refusing to use the sails in all possible cases and to be patient when there is calm. If you can do this, you can still be comfortable. So this is a mindset and perspective that needs to change, not an increase in battery storage density.

Interior heating

Stove top cooking
Oven cooking

I get all 3 of these by a wood stove. I throw stove away at end of winter and build a new one in november every year, it takes about a day to build one. I can cut enough wood for a week in less than an hour, and this type of heat reduces humidity in the boat a huge amount. It is also the safest and cheapest and really the only viable way I have found to heat the boat without using fuels (which are worse anyway even if this were not cheating)



I also have an evacuuated tube solar oven and it cooks even when it's below freezing, but takes twice as long as a hot summer day. I'm surprised thses are not more common, because in the summer months, it is the only thing I needed for cooking and really it's quite small and not expensive, and it is also self-cleaning because it's always on so it burns anything left inside into dust like a cleaning cycle.

Domestic hot wateror
Refrigeration

Everything you put inside a refrigerate doesn't taste as good, and it degrades the quality and freshness of food. There are much smarter ways to preserve food that don't require continuous energy. I would not want a refrigerator even if it were for free and did not use any energy.

I’ve done testing on the relative efficiency of butane vs induction stovetop cooking. Butane was about 50%, induction about 75%. Directly the only thing this is relevant to is determining that gas puts twice the heat into the boat while cooking, which is a consideration

You are not considering that only about 25% of the energy used to make the butane is available in the butane since most of it is consumed in the refinery, compression and transportation of the fuel and all the infrastructure required to support that. despite this, your figures of 50% or 75% show that neither system is very efficient. Both could have better than 90% efficiency but this is just now how most systems are designed.


If you are actually comparing using propane/butane for cooking (which is basically stealing from future generations) when there are plenty of alternatives available, you might as well compare the efficiency and cost of using slaves to row your boat around for propulsion and consider all the other useful tasks they could do for you without considering any moral implications.

[valhalla360]

Originally Posted by sailingharry

It was a hypothetical use case, but I was trying to be low, not high.

My Sabre 34, with a 23HP Volvo (underpowered) was normally run at close to WOT just to get decent speeds (near 6kts). It used .5 GPH, so 5 hours was 2.5 Gal and I'm pretty sure I was using mid-teens HP.

Wow, running at WOT to make 6kts. Is the bottom growth bad or just a horribly inefficient hull shape?

Our 34ft Gemini with 25hp outboard would do 6.5kt at less than half throttle. I realize it's a catamaran but not a terribly sporty one and we were loaded for liveaboard. Only time we needed to get close to WOT is if we were steaming into a 30kt headwind or such.

[Adelie]

Originally Posted by sailingharry

Plugging in isn't as easy as it sounds. I just did some math. Assume you want to motor with 10HP for 5 hours, and then recharge at a dock. That's 35KWh (10HPx700W/HPx5h). A typical 30A shore power cable is good for around 3KW. ......

1hp is 746W so 37.3kWhr.
Plus entropy losses so figure 40kWhr.

[Adelie]

Originally Posted by sailingharry

......
My Sabre 34, with a 23HP Volvo (underpowered) was normally run at close to WOT just to get decent speeds (near 6kts). It used .5 GPH, so 5 hours was 2.5 Gal and I'm pretty sure I was using mid-teens HP.
......

Originally Posted by valhalla360

Wow, running at WOT to make 6kts. Is the bottom growth bad or just a horribly inefficient hull shape?

.......

My guess is that SH was probably prop’d wrong.

I have a friend with a Cal 34 and I believe they could make 7kt or so using an Atomic-4 which puts out 18 or 30hp depending on exact model.

I am considering buying one and converting to electric propulsion(EP). From discussions with the motor vendor the vessel should be able to make 7.2kt using just under 10kW.

0.5gal/hr means a diesel is producing something near 9hp, which would be about right for 6kt in flat water.

If 9hp is near WOT for a 23hp motor then the problem is the prop not letting the motor rev high enough. If it was growth on the hull restricting speed then the engine would rev high enough to generate higher horsepower and it would show in the fuel burn. 23hp would burn something near 1.25gal/hr.

[sailingharry]

Originally Posted by Adelie

My guess is that SH was probably prop’d wrong.

I have a friend with a Cal 34 and I believe they could make 7kt or so using an Atomic-4 which puts out 18 or 30hp depending on exact model.

I am considering buying one and converting to electric propulsion(EP). From discussions with the motor vendor the vessel should be able to make 7.2kt using just under 10kW.

0.5gal/hr means a diesel is producing something near 9hp, which would be about right for 6kt in flat water.

If 9hp is near WOT for a 23hp motor then the problem is the prop not letting the motor rev high enough. If it was growth on the hull restricting speed then the engine would rev high enough to generate higher horsepower and it would show in the fuel burn. 23hp would burn something near 1.25gal/hr.

Adelie,


Curious where you get your GPM/hp numbers. If they are credible, it's really useful information.


I'm a little skeptical though (and with the research you do, I'm only a LITTLE skeptical, because you don't talk rubbish!).


I was for a few years overpropped, then under propped, and then finally got a Kiwi and dialed it in. But getting useful historical information on actual numbers when you use less than 50 gallons a year is challenging. Still, I was getting fairly consistent .5 GPM.


Now I've got a new boat, with a 55HP motor. I'm about perfectly propped -- I am about 100 RPM below redline at WOT. I run at least 80% redline routinely, yet I consume under 1GPM -- does that mean I'm running under 50% HP? I realize that actual HP is dictated by the load, not the available HP at a give RPM (just like Amps from an Alt are determined by what the battery will take, not what the alt will give). But that raises questions about the power vs speed curve, which we know is very hockey-stick shaped. Perhaps it takes the full 55 HP to give me 7.5kts, and my cruising speed of 7kts only takes 15 HP -- not beyond the realm of reason! But I'm not going to run multiple consumption experiements -- run 10 hours at WOT, refill tanks and calculate, run 10 hours at 90%, 80%, etc. To get 10 hours on my engine will include no-load battery charging, light load anchor up/down, harbor passages, etc, making it hard to suss out the actual consumption.



It sure would be wonderful if you could put useful instrumentation on a diesel for less than ridiculous cost. I'd love to see instantaneous GPH, so I could do MPG calculations on the fly. But I can't find them for less than $thousands.

[sailingharry]

I'll answer my own question!


Adelie, it seems your HP vs GPH numbers are in the realm of reason (no ballpark number for this will ever be terribly close, as there are too many factors -- but approxmiations are very useful).

This chart:
https://barringtondieselclub.co.za/t...-aspirated.pdf
is worth bookmarking. It provides HP vs GPH for naturally aspirated diesel engines. The numbers are close to the numbers you were suggesting.


One useful bit of information that lends credibility to the EP argument that diesel engines are massively over-spec'd. Both of my boats seem to have been only tapping 50% or less of the engine HP. That doesn't mean it's not THERE if I wanted it, only that I chose not to use it.
My Sabre 34 with 22 HP was, day in and day out, using around 10 HP.
My Saga 43 with 55 HP is, day in and day out, using around 18 HP.


Interesting data. Although, while I don't routinely run any engine at WOT for lengthy runs (the EP argument), I DO routinely run my engines at WOT during maneuvering. I like to stop when I say stop, I like a big kick of prop wash (or prop walk, as well) to push the stern, etc. But that's measured in seconds, not hours.

[wingssail]

Originally Posted by sailingharry

...It sure would be wonderful if you could put useful instrumentation on a diesel for less than ridiculous cost. I'd love to see instantaneous GPH, so I could do MPG calculations on the fly. But I can't find them for less than $thousands.

You could built a jury rig system to measure this. Tap into the fuel line between the tank and the engine and put a three way valve so you can pull fuel from the tank or another source (like a beaker with measurement marks).

Also tap into the fuel return line to be able to to divert the return fuel also int the beaker.

Fill the beaker with 1 ltr of fuel, turn the valves, and measure the number of seconds it takes to use a certain amount of fuel.

You could do it at the dock.

I've not done this, instead I've carefully built a spreadsheet with fuel consumption and knots of boat speed over several years, it is pretty accurate although I had to start over when I changed propellers.

RPM G/hr L/hr Speed MPG
1000 0.18 0.661396885 2.0 11.3
1100 0.24 0.881862513 2.9 12.2
1200 0.26 0.970048764 3.4 13.0
1300 0.28 1.05963 3.6 12.7
1400 0.30 1.14114 3.8 12.6
1500 0.31 1.1615175 4.1 13.2
1600 0.36 1.3408395 4.3 12.1
1650 0.40 1.516086 4.5 11.2
1700 0.45 1.687257 4.8 10.7
1800 0.49 1.833975 5.0 10.3
1850 0.52 1.9366776 5.2 10.0
1900 0.55 2.04467835 5.5 10.1
2000 0.57 2.1380073 5.8 10.1
2100 0.61 2.2863555 6.0 9.8
2200 0.70 2.631354279 6.1 8.7
2300 0.76 2.867949172 6.2 8.1
2400 0.87 3.279758625 6.3 7.1
2500 0.99 3.716856 6.3 6.4
2600 1.16 4.360785 6.4 5.5
2700 1.30 4.8906 6.5 5.0
2800 1.47 5.501925 6.6 4.5
2900 1.63 6.11325 6.7 4.1
3000 1.83 6.84684 6.9 3.8
3100 1.96 7.3359 7.1 3.6
3200 2.15 8.06949 7.2 3.3

[Adelie]

Originally Posted by wingssail

You could built a jury rig system to measure this. Tap into the fuel line between the tank and the engine and put a three way valve so you can pull fuel from the tank or another source (like a beaker with measurement marks).

Also tap into the fuel return line to be able to to divert the return fuel also int the beaker.

Fill the beaker with 1 ltr of fuel, turn the valves, and measure the number of seconds it takes to use a certain amount of fuel.

You could do it at the dock.

I've not done this, instead I've carefully built a spreadsheet with fuel consumption and knots of boat speed over several years, it is pretty accurate although I had to start over when I changed propellers.

RPM G/hr L/hr Speed MPG
1000 0.18 0.661396885 2.0 11.3
1100 0.24 0.881862513 2.9 12.2
1200 0.26 0.970048764 3.4 13.0
1300 0.28 1.05963 3.6 12.7
1400 0.30 1.14114 3.8 12.6
1500 0.31 1.1615175 4.1 13.2
1600 0.36 1.3408395 4.3 12.1
1650 0.40 1.516086 4.5 11.2
1700 0.45 1.687257 4.8 10.7
1800 0.49 1.833975 5.0 10.3
1850 0.52 1.9366776 5.2 10.0
1900 0.55 2.04467835 5.5 10.1
2000 0.57 2.1380073 5.8 10.1
2100 0.61 2.2863555 6.0 9.8
2200 0.70 2.631354279 6.1 8.7
2300 0.76 2.867949172 6.2 8.1
2400 0.87 3.279758625 6.3 7.1
2500 0.99 3.716856 6.3 6.4
2600 1.16 4.360785 6.4 5.5
2700 1.30 4.8906 6.5 5.0
2800 1.47 5.501925 6.6 4.5
2900 1.63 6.11325 6.7 4.1
3000 1.83 6.84684 6.9 3.8
3100 1.96 7.3359 7.1 3.6
3200 2.15 8.06949 7.2 3.3

Serendipity 43.
What engine?
That's really good data.

[Adelie]

Originally Posted by sailingharry

Adelie,


Curious where you get your GPM/hp numbers. If they are credible, it's really useful information.


I'm a little skeptical though (and with the research you do, I'm only a LITTLE skeptical, because you don't talk rubbish!).


I was for a few years overpropped, then under propped, and then finally got a Kiwi and dialed it in. But getting useful historical information on actual numbers when you use less than 50 gallons a year is challenging. Still, I was getting fairly consistent .5 GPM.


Now I've got a new boat, with a 55HP motor. I'm about perfectly propped -- I am about 100 RPM below redline at WOT. I run at least 80% redline routinely, yet I consume under 1GPM -- does that mean I'm running under 50% HP? I realize that actual HP is dictated by the load, not the available HP at a give RPM (just like Amps from an Alt are determined by what the battery will take, not what the alt will give). But that raises questions about the power vs speed curve, which we know is very hockey-stick shaped. Perhaps it takes the full 55 HP to give me 7.5kts, and my cruising speed of 7kts only takes 15 HP -- not beyond the realm of reason! But I'm not going to run multiple consumption experiements -- run 10 hours at WOT, refill tanks and calculate, run 10 hours at 90%, 80%, etc. To get 10 hours on my engine will include no-load battery charging, light load anchor up/down, harbor passages, etc, making it hard to suss out the actual consumption.



It sure would be wonderful if you could put useful instrumentation on a diesel for less than ridiculous cost. I'd love to see instantaneous GPH, so I could do MPG calculations on the fly. But I can't find them for less than $thousands.

Thanks for the compliment.

I got the diesel: 18 hp-hr/gal number from a book by John Vigor.
In the last several days I have been arguing this number with somebody in another thread. In researching that argument I've looked at the engine specs for 4 2l Yanmar engines. Using the gal/hr and prop power curves I calced fuel consumption at 17-19 hp-hr/gal.
3 of the engines are calc'd in this post: https://www.cruisersforum.com/forums...ml#post3308442

This site indicates about 20hp-hr/gal and has numbers for gas engines (11-12hp-hr/gal) and 2-stroke outboards (6-8 hp-hr/gal).
https://www.sbmar.com/articles/fuel-and-horsepower/
I'm dubious about turbos being significantly more fuel efficient than naturally aspirated. The turbo work energy all seems geared to cramming more air into the intake side so more fuel can be burned and they can get more hp out of a given size engine. In the 1940s & 1950 there were Compound-turbos on aircraft where the waste energy in the exhaust was scavenged to add more power to the output directly, so no extra fuel and in that case fuel economy improved. Then we transitioned to jet engines which only in the last decade or so have gotten to the same point in fuel economy.

When you look at engine data, you need to look at the prop curve to determine how much power you are using, it looks like the drag curve. Yanmar puts the engine and "ideal" prop curves on the same chart so when you look at it you can see what the engine could make at a give rpm vs what the prop can use and accept. In prop-engine design the goal is to have them meet at or near the point where the engine is at max rpm/max hp. Otherwise the engine is over- or under-propped.

Due to their higher fuels prices the Europeans went with Controllable Pitch props long ago. The extra cost and complexity was offset by increased fuel efficiency at most operating speeds. Such props even made it onto sailboats, early to middle Albin Vegas had them.

The US with lower fuel costs had no financial incentive to replace the cheaper fixed pitch props.

I understand about the price of good fuel flow meters. I have a friend with a Flowscan fuel meter on his sailboat, but he got it because he worked at Flowscan.

I intend, at some point, to test fuel flow for my new outboard. I'm going to get a clear hose, mark it at 5ml increments filling it from a graduated syringe. and hook that to the standard hose fitting my engine uses. Hang the hose up the backstay a bit. Overfill it some so that I can get up to speed before each test starts, then time it for consumption of 15 or 30 or whatever ml of fuel, the longer the run the more precise the result. I have a tach for the motor so I can relate fuel use to engine rpm. And using speed from GPS I can calculate mpg. Currently the boat is dry sailed so it is very clean. Whenever the boat get a berth in the water I can can then monitor rpm vs speed to gauge how bad the bottom growth has gotten.

[wingssail]

Originally Posted by Adelie

Serendipity 43.
What engine?
That's really good data.

Yanmar 3JH2E, 35 Continuous HP, 38 Maximum. At 2000RPM Yanmar suggests it is producing about 20 HP.

We have a 2.83:1 (non-standard) reduction gear and a 2 blade 18" diameter 17" pitch propeller, both of which affect how much speed we get for a given engine RPM. This reduction gear allows a much slower shaft and propeller speed.

Our vessel has a very easily driven hull form. At 2000 RPM (20 HP) we get a speed of 5.8 knots and use .57 gallons of fuel per hour for 10 nautical miles per gallon.

This works out to be about 35hp/gal at 2000RPM.

I believe that it would take 15000- 16000 watts to propel our boat at 5.8 knots, an easy cruising speed.