Tech Review: After a year, a rundown on the gas to electric motor conversion on my sailboat

After a year and the number and type of questions I received I thought it would be a useful to provide a rundown on the electric motor conversion. I created this episode, number 75, and talked out the pertinent points.

If you want to see the play by play then I suggest watching Season 1 where I gutted the boat and got the old Atomic 4 working, Season 2 where I did the original conversion, and Season 3 where I changed some things based on what I learned first hand.

Atomic 4

My original motor, the Atomic 4, is the traditional gasoline powered motor that the Hughes / North Star 1500/35 was fitted with in the 70’s. You can still buy parts and receive servicing from many mechanics including Moyer Marine.

My particular motor in fact had needed repair when I originally purchased Northern Comfort.

When I bought the boat, it didn’t have a working motor. It wasn’t seized but I was told it was ‘irreparable’. What I learned was that it has no compression in all 4 cylinders. I was actually surprised and initially thought my compression tool was broken, so I drove to Canadian Tiore to buy another one, and then after testing again I was pretty confused to get the same test readings.

I later learned that the water muffler was removed and that exhaust cooling water had backwashed into the valves and into the oil pan.

Once I got the boat back to my shop I started taking the head off and I then realized that as a core problem the head gasket was blown between cylinders 1 and 2 and between cylinders 3 and 4. Water doesn’t compress and the backwash problem was the root cause.

I actually has 2 aftermarket gaskets in the set of scrap materials that came with the boat so after a thorough cleaning, 5 oil changes to remove the water and replacing the gaskets I was able to get the motor running. It was pretty smooth actually.

In my first year, but was mid season and I was eager to launch. Northern Comfort was powered on this Atomic 4.

What I learned that year was that the engine was hugely loud, smelly, and I could see some fuel and oil leaked into the bilge. I filled it up and burned 4 gallons, almost 1/2 tank, on my first motor sail and I decided after motoring that there had to be a better engine. I was fearful of gas leaking and fumes exploding. The engine vibration was largely felt in the cockpit under my feet.

Choosing an Electric Motor

I wasn’t 100% certain what I wanted in an electric motor. I heard about regen, where the motor turning by the motion of the boat and wind acts like a generator. I heard about AC Motors, DC motors, brushless motors. There are whole complete packages like you can buy from Electric Yacht and Ocean Volt. There are also semi DIY packages from companies like Thunderstruck that produce parts that go together.

I realized that I didn’t know why I wanted certain components 100% but I did have a good idea.

I knew that most electric motors are designed to run at certain RPMs for efficiency. I didn’t want a high RPM revving motor as my prop was used to running at 1500 to 2000 RPM. So I wanted a low speed electric motor and everything I read basically said that I wanted to run at 3.5 knots. Anything more speed than that I learned that the energy required was not proportional to the resulting boat speed.

Golden Motor

One of the factors I wanted was to buy from someone local, so I can get some localized help if I needed it. The other was that I am a hands-on DIY guy and I wanted to learn as much as I could about this, and install it myself.

Golden Motor offers a number of electric motors for various conversions and although the Canada outfit focused on e-bikes they had a number of conversions listed on their website. They were helpful figuring out the motor and I knew I could drive there to pick up more parts if I had to. I was prepared to go into the unknown.

I did the rough calculations based off of horsepower. My Atomic 4 although rated as 25 to 30hp, I knew that gasoline engines are very inefficient and that 30hp likely translated to 8 to 10hp by the time it was at the prop, especially at lower RPMs. Most gas engines you have to rev to get the higher horsepower.

Most electric motors are actually very efficient as compared to traditional combustion engines. I decided that DC power was better than AC power simply due to batteries in a boat being DC. It can easily be argued that these BLDC electric motors are actually AC motors with a DC wrap on them but they operate as DC from the perspective of the incoming power.

Being more efficient translates into less power required in to get more power out as compared to gas or diesel. By my understanding, the 5KW motor is about 7 horsepower and the 10KW about 14hp. I reviewed the torque rating of each motor and realized that it took less energy to turn the 10KW as compared to the 5KW at the same RPM/Power. So as my usual practice is to buy more than I need, I decided on the 10KW and I am glad today that I did make that decision as I would later learn based on my motoring habits.

I decided that brushless was better than brushes as there is no chance of any spark coming form the motor and long term maintenance of BLDC motors is much better suited to boat life.

I didn’t know much about the controller, so I went with the Golden Motor recommended matching part, the VEC-500 Vector Controller provided by the same company.

Cost was also a major factor as I was prepared to use this solution as the cost of my education and I very well might be ripping everything out and starting again at some point. There was so little information, just a few YouTube videos about DIY conversions, and they didn’t have brushless DC motors. I wanted to learn about it, what was important and what wasn’t, and and I was able to pick up these as about cheap as I could get. They

So I received my electric motor (you can view the details on my unboxing video) and started wondering how to power it up as I didn’t have 48v worth of batteries lol.

I remember being both anxious and unnerved. Did I just sink $2000 into something that I would never get working?

The Gas to Electric Motor Conversion

1st, I had to get the old motor out. The guys at Harbour West Marina helped me out and the cost wasn’t too bad, an hour of their time.

I had no choice but to take apart the settee and captains table to get the tank out and then discovered that the floors (supporting the cabin sole) were rotten. This was a boat from 1975, so I was prepared for the worse. I ended up cutting out the entire cabin sole and replacing all the floors.

If you are going to do a job, do it right. Don’t cut corners.

So my engine conversion took a turn and I was rebuilding an entire cabin at that point. Might as well renovate the galley too, right? Get rid of the propane lines, the old legacy freezer and go electric!

Once I got the engine area cleaned up I realized that there were some basic things I needed to go electric.

• Electric Motor
• Controller
• Throttle
• Batteries
• Battery Monitor
• Solar Power
• Fire Extinguishers

After pulling out the motor I started working on how to make a frame to attach the electric motor, and decided that everything I read stated to have a 2:1 ratio of motor to prop reduction. The Electric motor had to run at a certain speed to be efficient and the torque.

I found some pulleys and the right belt using the engineering tool on the Toronto Gear website. It was a very useful resource to someone wanting to DIY. I ordered the matching parts and picked them up in Scarborough. I then finished the fiberglass plate as a template/first draft of the mount and then started mounting them.

I had some issues with tension and the belt skipping until I got the alignment right. It was finicky and the motor mounted too far from the shaft. I also learned that I should have made the mount based off the shaft, not the original motor angle. I was close, but no cigar!

But it did work!!! I am learning about my electric motor conversion.

Lessons Learned

That 1st motor mount worked fine once I got it tweaked, and it took 4 different redesigns to get my lower pulley fixed and the thrust of the motor under control. I actually broke the lower pulley mount the day I launched and had to get towed back to dock.

I was pretty embarrassed but happy to get in the water at the same time. The guys on dock were looking at me a little strange when I yelled back to them that I needed help 100′ off the launch.

The alignment was critical. Any slight misalignment is a critical error. I touched on some points of this in my Lesson’s Learned video. I ran for a while with a very slight misalignments and the belt tension actually broke the upper pulley belt guide off it. I almost lost my motor underway when that happened. I mangled to get a working temp solution while underway and limped back to the marina.

I also didn’t like the noise. The timing belt I used made a groove sound while underway and it vibrated. I ended up in year 3 making a completely new mount based off of 1/4″ stiffed aluminium for the base plate mount. I welded my own frame mount as you can see to the right here in my video documenting the build for my electric motor conversion. I am not professing to be an expert welder, doesn’t look pretty but it’s damned strong.

I learned that a stiff collar 1″ to 7/8″ wasn’t the right choice. I need a flex coupler of some sort to take out any slight misalignment. As hard as I tried I could not get that motor 100% bang on straight with the shaft. Once I put in a jar coupler, with flexible neoprene spider gear in the middle, I was in much better shape.

The other thing I wanted to change is the shaft collar locks. I only had one on each side of the pulley in the 1st version and I wanted to have 2. So I made the mount with enough space to have 2 locking shaft collars on each side of the pulley. Although only 1 worked in the 1st version I was always worried if that collar slipped. When the prop is pushing against the water, the energy translates as shaft thrust. The pulley is fixed and that is where it doesn’t move. I just felt more peace of mind by having two instead of one.

Batteries

Not knowing much about battery systems, I went with lead acid wet deep cell 225Ah 6v golf cart batteries. This was 100% because I was so uncertain about what I needed I just wanted to get 48 volts and over 200 amp hours. I knew that I could not run them hard, anything over 25 amps would start to reduce significantly the life of the batteries.

This wasn’t exactly the best choice, but they were cheap and I wanted to get out on the water. My electric motor conversion required energy storage of some type and I didn’t want to splurge on Lithium until I knew why through first hand knowledge. Cost a major factor and I also didn’t have to wait, I could pick them up myself in a day.

From the average point of view they worked fine. I have had these 2 years now and they are still going.

My limitation however on the 25 amp draw had me reaching for ways to be more efficient in my use. At 25 amps I can get to 3 knots boat speed which under most circumstances is fine. If an emergency arises or some other need like staying ahead of a tanker (more on that later) in the left bridge canal drives the need to reach 5 knots, then I need 90 amps draw rate which is far outside these lead acid batteries.

I need lithium.

I am leaning heavily towards Lithium batteries made by Thundersky but still undecided. From their website “The positive active material of water-based LYP battery is made of fluorine compound and rare earth, while the negative electrode active substance is made of nano-carbon fiber and artificial graphite. Therefore, it can keep its inherent molecular structure unchanged, lattice firm, impact resistance, high safety, wide temperature resistance and long service life during high current charging.”

There are some compelling reasons to use these, they are used in submarines, and they can output at a rate 200 amps which is double my need. The charge rate is also quick, so if used in combination with a Quattro from Victron Energy I will be able to run a generator and should be able to charge quickly and run under motor for a long time if required to get through a canal, bridge or just want to motor in excess of my battery supply.

I also understand that the charge rate is also much better as compared to AGM or Lead Acid batteries.

As I learn more about batteries I will update this page.

After testing 3 different batter monitors (cheap Chinese DROC, Renogy and Vcitron), Victron Energy is the clear winner in terms of product design and application. I love the blue tooth of my BMV-712 and I am working on getting the data into my Raymarine MFD. Victron Energy makes a very robust product compared to other brands I tested.

Charging your Electric Motor Conversion

As a last component of the electric motor conversion, charging and battery management is being done with some Renogy panels. I originally bought a single 100 watt panel and ran with this for a while but figured out that I needed more. I bought 3 more, rigged up an install on top of my Bimini and I would say for the most part, if you are patient they will work fine.

I also want to cook with the induction cooktop, and the sun just isn’t at a good angle for very long in Canada so I am adding in an additional 400 watts by adding an arch and making some custom mounts.

I had to buy some shore chargers so that I could equalize the batteries. I bought some NOCO Genius 2 chargers and they take a few days (3) to get from a really bade state to a full charge. In the early season and late season I have to use these in conjunction with my solar to stay topped up.

I am thinking that when I have the Quattro, lithium, and a generator these will all get ripped out and replaced so I can charge at a 35amp rate instead of 2 amp rate. Less wires, less clutter and get back to a full charge burning less fuel while off grid.

Summary

While this write-up is mainly just a sharing of information on my electric motor conversion, I also wanted to pass on some remarks on my satisfaction level.

I am enjoying learning, pressing my knowledge limits and really engaged with the feedback I am receiving online. There is still a lack of concise information out there, and a lot of opinions including mine. I am however documenting everything on my channel and I will be heading out to the Maritimes in 2022.

So far I would never go back to gas (or diesel) due to the way I use it. If you want to just motor somewhere and are stuck to a schedule, then I am not certain electric would be the best choice.

For myself, I am not on a schedule, don’t have to be anywhere soon, and can read the weather patterns and do my best to sail in decent conditions. If I have a storm brewing up, I am ok with sailing through it or finding shelter and battening down and weathering it out.

I am impressed with the torque of the 10KW brushless BLDC motor at lower RPMs. I believe with a new prop that better matches this motor I won’t have as much cavitation and better thrust efficiency at lower RPMs. I am now using about 1000 watts to run 3.5 knots with my direct drive mount so I am starting to hit my energy consumption / rate of speed goals.

I don’t have to fill up, and I don’t have to worry about running out of gas. I still have to closely monitor my rate of consumption but that can be improved on. As new battery technologies come about I will still be able to use this motor so I think the choice was good (for me).

You do have to be handy however, and if you wanted outside support a company like Ocean Volt might be a better choice. Boat life for me is more about being self reliant, and this solution suits me. I am able to putt along at 3 knots for about 4 hours now with my cheap lead acid batteries. I am excited about the future of silently propelling along my journey.