[7.16.19]  High Power Electric Outboard: V2

This project centers around reviving a 1983 evinrude 35hp long-shaft outboard and converting to electric. The outboard was heavily corroded but was the right price (free). Follow along for the disassembly, repair and electrification. Future plottings, CAD files and diagrams included below. 

Outboard Recovery Part 1
Cleaning and Prep Time for Paint Brushless Motor Mounting First Test Testing Notes Conclusion Image Directory

Quick Overview

The goal of this project is to take a recycled outboard with a 'well past seized' engine, restore it to working order and convert to electric. A fairly sizeable, battlebots-grade brushless three-phase motor and some high powered batteries will hopefully propel things along. In the process i'm aiming to gather data on the performance of the craft under a variety of configurations.

Either way here's some footage of the craft after the conversion was complete, some zooming about local boatable waterways was had.  

Attempts at recovering the outboard

Here's the outboard host, fresh from its trip back from New Hampshire. An excellent comrade helped out by grabbing it from the, more local, seller. Its fiberglass cover did a good job at hiding the engine's state of sadness. It was quite far gone, there was no chance that even the finest in combustion-izers could resuscitate this beast. It did have a few things going for it, everything below the engine looked in good condition. This only makes sense if the engine was stored, upside down, with its fiberglass engine cover filled with water. Bizarre.
This is what the engine is supposed to look like [link]
The outboard came from the magical craigslist, and was picked up by ever excellent, Ted of New Hampshire. We spent a solid 3 hours in miters trying to de-engine the beast. Bolts were sawed off, drilled out and everything that should have removed it was removed. A couple dozen sledge-hammer blows were applied to 'loosen' the engine from its outboard clutches, to no avail the engine blob was stuck. 
Fast forward ~6 months, the outboard with the very sad engine had been sitting in a stairwell. Now that it was summer I began plotting power boating. Time to re-evaluate 'free giant outboard'. It was dragged onto the bench and stared at. Ooof Its worse than I recalled. 
The hammer blows are all the more visible here, a significant amount of force was applied. That engine was really stuck in place, prying with crowbars, vibrating with power drivers, nothing budged this thing. We all took out frustrations with sledgehammer blows of varying angle of attack. Corrosion is quite a bother. 
The question kept popping up, how did it get so corroded? I seriously am a befoogled. Its almost as if it was planted upside down in the soil, in order to grow more outboards. Bizarre. 
The NRL "absolutely giant band saw" got a chance to show off. The entire outboard fit between it's giant jaws and over the course of 42 minutes the engine and outboard were separated. 
This wasn't easy, the outboard itself is 'swoopy' and curvy, clamping it required some curious wood structures to capture everything and keep the outboard level. Finally the outboard was sawed from both sides, flipped over about 1/3 of the way through from the first cut.
42 long minutes later
The outboard engine was removed. I was really concerned about the hardened shaft between the engine and the outboard, but fortunately tugging and loosening from the propeller end of the outboard really helped things. 
Look at that for a second.
The saw was about 1/8 of an inch from the shaft and cut just in the right spot. Quite excellent! Welcome to the outboard cross section.
The un-supported engine remnants clonked onto the floor and were heaved into a recycling dumpster. Nothing immediately identifiable was worth anything, the mating spline appeared to be directly welded to the engine assembly. 
Outboard on a hand truck.
Behold a long shaft outboard on a hand truck. Time for some motor plotting. There are some options here, given that this particular outboard was rated for a 26kw engine, there is plenty of room for either high rpm automotive alternators (Buick lacrosse hybrid motor) or even the famed go kart 'alter-moter' used in the miters go kart. plenty of options afoot, but ideally keeping the mass and complexity down would be ideal. 'Debugging at sea' is not advisable. 
With the engine FORCIBLY removed, I took a look at the shaft. Its a curious size, 5/8 outer diameter - 14 tooth splined shaft. After a few measurements I generated a water jet cut file for a homemade adapter. 
Quite good! the spline cutout fit great! I used 1/4" thick 6061 aluminum with 3 holes for pins, with a stacked spline adapter plotted. Very excited when this 'just fit'. This was going to be a curious one to make an adapter. I hemmed and hawed about how I wanted to approach machining this part. 
Holey moleys, are you kidding me, JUST THE RIGHT SPLINE fitting, for quite cheap. As it turns out ITS EVEN STEEL. I ordered two and lo, they fit like a glove! excellent! Shown far right are either side of the splined adapter. 
Here's the outboard in its constituent parts, pulled from the boat mount. Nominally this is the right-angle drive and the long shaft housing, finally separated from the outboard assembly. 
The shaft had seen better days and was a might corroded. Attempts were made at spot-cleaning the rust off, but this was the deep-pitted kind :/ By eye the shaft also didn't quite look straight but that will be addressed later on. 
The right angle drive also contained some putrid smelling oil which was drained out and flushed (temporairally) with Jeep gear case oil. The proper evinrude gearbox oil was not immediately available so jeep gear case oil was used as it was easier to acquire (auto zone) and features a convenient squirt nozzle.
So next up was to possibly replace the bearing seals and or inspect the bearings. I made a tool to yank on the internal threads against the case. This did not work at all, everything in there was seized to the case, as in, impact driver going full tilt was not moving anything. So for the time being the bearings and seals are 'decent enough'.
Ok lets take a look at the splined drive shaft. To do this i mounted the shaft in a 3-jaw chuck in an older clausing lathe, with the live center as a reference. Yep it was quite sad and rusty, shown in the video below. 
Its amazing that a brand new shaft for a ~30+ old year outboard is available with 2 day delivery. The new shaft bore the same model number engraving and appeared to be form and function identical. Quite an excellent finish for a 30$ ebay part.

Outboard Shaft wobble
As its fairly visible in the video, the shaft that mates the lower end to the engine was quite sad. The live center on the lathe is collinear with the center axis of the chuck, so any deviations indicate that the device in the chuck is not 'centered'.  What i don't quite understand is how this got so bad. Either way this wasn't going to do for any reasonable amount of operation. I managed to find a vendor selling replacement shafts (ebay) and it was impressively better with the new shaft mounted.

Grime and Paint removal
The first round of paint removal begins, a cart covered with thin plastic painting drop-cloth was used to contain the mess. Citristrip spray was used as these parts have a lot of tiny areas that hand-painting would be difficult to get to. Nominally I also wanted to test the effectiveness of the spray version of citristrip.
Release the goo
The pink goo was painted on fairly heavily to both the outboard shaft shroud and the right angle gearbox. I did not have enough spray to do the transom mount at this time, so that would be tackled later. I was aided in this quest of de-painting by Sam and some NRL colleagues. 
Some elbow grease and scraping later...
Here's the outboard shaft shroud after scrapping, wire brushing and scrubbing. I was quite excited about this, and began plotting if anodizing the whole thing would be feasible, but determined it would be quite a huge bath of sulfuric acid.  Quite happy with the results of the cleaning.
The right angle gearbox was a bit more difficult, while the spray seemed to remove most of the paint, a lot of primer still stuck in crevices, and a normal wire brush didn't quite do the trick

I wanted to reach into smaller spots with something coerce, but most of the online parts i found were fairly lacking in the 'hudspeth' department. I opted for a wire brush intended for an angle grinder, and instead of using it in an angle grinder, i turned down a bolt with the same thread pitch as the angle grinder. This allowed a normal drill chuck to take the part without much trouble.
After a lot of drill-bruising and scraping and hand scrubbing, the parts needed another coat of pink-goo to attack the primer layer that remained in some areas. Shown here is a ventilated room with the parts sitting to be de-painted
This was a silly aside: Can you use compressed air and water, in a siphon, to blast off loosened paint? The answer is 'probably' but at 100psi, not really. This is a compressed air siphon gun that I used instead of a power washer, as I did not have a power washer handy. I made the mistake of letting the paint remover sit for ~5 days. It re-hardened into a pink film and was way more difficult to remove than I had initially  imagined.
After the failure of siphon-gun, i applied more pink goo to loosen up the hardened pink goo. The parts sat and de-painted for 12 hours. The muck is quite impressively messy. 
The primer was now coming off again and with the application of wire-brush wheel and a lot of scrubbing, the parts were de-grunged, and they looked quite happy. 
The propeller, was also in need of some cleaning. The splined coupling was taped over and the whole propeller was epoxy-primered. In retrospect the zinc spray may need a lot longer than the advertised time to set, even in a warm environment. 
More drill-scrubbing ahoy and the outboard right angle gearbox emerges with precious bare-metal. Note the vice in this photo is very lightly grabbing the whole unit. A rather precarious stand was used to hold it in place while the primer coat was applied. Note this photo was taken after the tape covering the outboard shaft was removed.
The second to last hard part: the outboard steering thing. This had a lot of mold cavities and required tiny-scrubby-brush action for a few hours. Sigh. Scrub Scrub Scrub. The cavities were too small for the drill brush, so manual scrubbing it is.
The hardest part was upon us, the transom mount, full of hard to reach cavities that somewhat contained goop remnants. To attempt to get any remaining surface grime out of the part, I mixed up a soupy bucket of simple-green ~degreaser. A motor with an offset mass was attached to the bucket and it vibrated on its own while run from a variable power supply.
After ~10 or 15 minutes of vibrations, the part was pulled out. Quite good. The pink remover remnants were removed and aside from some touch-up with the scrubby brush, the transom mount was ready for priming and painting!
This took three re-positioning to get full coverage, but the transom was now primer-coated. The two wubby-mounted parts also were primed in the process. The primer was allowed 24 hours to set. The outboard parts are starting to come together!
Tying up and preparing for paint
Parts were inspected for un-primered areas and touched up. I opted to primer ~4" into the former exhaust cavity in either direction to maintain a reasonable amount of corrosion protection. 

Vibratory washing
This was a bit of a silly exercise in cleaning all of the inset parts of the aluminum casting. I used a small 24v dc motor and adding an offset mass to the shaft to make a realtivley low frequency oscillator. This worked surprisingly well, as the solvents in the janitor-bucket had an opportunity to jostled allowing more solvent in deep pocketed areas. Surprisingly given the bucket was on wheels, it seemed to still do quite well at washing and dissolving off paint and primer that was left on the casting.

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Painting The outboard Part 1: Respirators and cassette tape

I wanted to get the outboard up and assembled to get to work on the electronics and mechanicals. I didn't want to wait for online paint retailers so I purchased some epoxy based marine paint to cover the primered parts. I visited CG Edwards and grabbed an old, light blue paint kit. I hadn't known that they no longer actually carry paint, but are more of a shipping intermediary, so there were some quite limited options. IInitially, I didn't quite realize how old this marine epoxy paint was. The cassette was labeled 1993, yes the paint included an information cassette tape. Literally a cassette tape. 
This is a ventilated welding / paint room, where the rear part of the room has a negative pressure to take care of the fumes. Plastic garbage bags are used to keep the table clean, and make cleanup easy.
Protective Gear
As this epoxy paint was quite toxic and reccomended air filtration, fortunately pills hardware had some of these fancy respirator filters in stock. Yowzas, rated for acid gas? OK.
The painting began, a 'ratio metric container' was chosen and the mix of 3 parts paint 1 part hardener was used. Nominally this is supposed to be thinned by some hella-solvent that was probably sold in the 90's, however, due to not having that and reading about it after having set up, painting with the non-thinned mixture was attempted.
The epoxy paint claimed to 'set overnight' and get tacky within 3 hours, however, without the 20% thinning agent, it set QUITE QUICKLY and got quite sticky. Otherwise, the outboard painting went well, albeit slightly runny. Most of the parts were fully covered, some required a flip and paint ~12 hrs later.
If the parts were hanging, getting a better coat would be way less difficult, so, as things go, a makeshift clothesline of parts was born. With the dangling parts, easily re-positionable by glove, everything was covered. The thinned-out goo was quite lubricious and required a bit of paint drip mitigation. Otherwise everything was going swimingily.
Model # For Reference
I taped over (poorly apparently) the model and serial #, which are included here for reference. This does point toward this being a 35HP outboard, at 5500 RPM. Its hard to make out but this indicates that this outboard is an E35ELCSM Evinrude. There are still parts available online [link]
There are a surprising number of parts in this contraption. Shown right is an excerpt from a repair manual. Quite a lot of parts to make this thing work. Bearings bushings gaskets and seals oh my!  Given that the engine bit is, in its own, a huge pile of components just the lower is quite a bit of hardware. 
Here's the assortment of parts after sitting to dry for a weekend. Quite good all things told, the older marine paint seemed to still work well enough and all that was left was to clear out any plugged holes and mating surfaces and re-assemble.
One of the real challenges was the number of inside cavities and the like in a few of the parts, as a result there were a number of paint, flip, paint, etc. Still quite happy with how it turned out.
Everything cobbled back together somehow still resembled an outboard! The rubber vibration mounts had almost all succumbed to age and fallen apart, but should be rescued in a future episode.
There were some spots that didn't take well to painting, one of the adjustment levers got bound up with paint and when I moved the lever, it came un-done. The actual pivot that the boat makes was also quite resistive, admittedly its mounted a bit offset to a large steel table in this setup.

Motor Time! A large Brushless motor and a curious adapter
Time to start plotting a motor mount. A warm weekend beckons and this project has been sitting idle for a while.  I took a photo facing head-on with the outboard lower end and used it to mock up a solidworks drawing. 
For a first test, i found a reasonable host motor, an ME0907. This is a ~400 $ Brushless 3 phase motor, with a max rpm of 5000, 10mH of phase to phase inductance, and rated at 100A continuous at 48vdc. This gives us a rough 5kw nominal value, and a short duration peak of 10kw. While not enormous amount of power, its still sizable in comparison to an off the shelf 500 W trolling motor. This motor was also conviently 'free' from a lab clean out.  The benefit of the spline mount is, if there is a better motor available its simply a motor-mount change over. 
With a cut-out plate that matched up four motor-mount positions to the actual outboard lower-end, mating the two together became more of a reality. I did not have proper hex-bolts in the correct size, but fortunately had some extremely large flat-head screws that just fit. I mcmaster-carr'd the correct size bolts, but kept along with the screws for making sure everything fit together.
I made four aluminum risers to hold the motor a fixed height above the mounting plate. This distance is mostly defined by the space requirements of the spline adapter to the motor shaft. I needed enough space for both to mate well, while still having space for the spline adapter to be mechanically sound.
Here's the gap i ended up with (1/4 of an inch). The shaft adapter would sit mated to the motor side and slide onto the spline for attachment. This is nominally similar to how the engine possibly worked, as the engine had the remnants of a spline coupler.
Here's the whole setup sitting clamped to a table. A sheet of plywood was temporairally attached to a workbench for a rough mount. This allowed a rough actuation of the transom mount. The outboard itself is rather heavy, an electric actuator may be a good fit for adjusting pitch underway in the future. I think this outboard was normally setup for having a pin in one of the four lower mounting holes setting the rough 'ride height', but that particular pin was quite corroded in place and will probably end up getting chopped out.

Its starting to come together, just a bit of mechanical connections and electrical connections, right?
Time to make the spline adapter!
I grabbed some mild steel stock and used a boring bar on the mighty miters lathe to get a nice fit against the motor shaft. The keyed shaft will be locked in with three set screws. Ideally i would have used a key here but alas i did not have the hardware on hand.
Next up, I machined out a groove for a trimmed down spline adapter. The spline adapter material was a curious one. It wasn't technically hardened, but it also wasn't mild steel. It seemed like a really curious material and took a while to trim down. After a few minutes at the lathe i had turned a quite snug adapter that could accept the motor shaft on one side and the trimmed down spline face on the other. 
Shown is the spline insert in the motor shaft adapter. Some quick TIG welding later in DLAB, and the two were bonded snug-ly together. Note that some extra surface prep here would have helped as technically i was bonding dissimilar (unknown) spline metal with the mild steel round i was otherwise using. 
The motor spline adapter mounted to the motor and again mounted to the outboard. What i found fairly curious is the motenegy's max RPM range is fairly limited, resulting in it operating inside the engine RPM window. The actual 'nominal' engine rpm that the outboard was rated at is 5500, 35hp. This equates to 26kw, which is quite a bit higher than this motor is rated to 
Here's the Motor on its adapter plate.  Note that there are long flat-head screws in place here holding the motor to the mounting plate through the standoffs. These were intended to be actual hex head bolts, however a porch-thief managed to abscond with my package before i got to it. Congratulations porch thief you have five hex bolts. 
The motor is mounted, the shaft adapter in installed, and the propeller spins smoothly. This was quite a happy time as the upcoming warm weekend beckoned.The whole apparatus is quite heavy. While its still lift able by hand, its just quite awkward to move solo. The 'long shaft' topology is also fairly visible here, as the actual outboard is a bit huge.
While we're here lets take a gander at safety. As this is an aquatic application, keeping the operating voltage low is fairly optimal. This conflicts a bit with power requirements. It would be fantastic to put a 10+ kw Brushless motor on this outboard, but, operating in a ~60v or lower threshold the current requirements start to get fairly ridiculous.
Power Desired [KW]DC Link VoltageDC Link CurrentDC Link Wire GaugeMotor Phase Wire Gauge
56083 A
1060166 A
1560250 A
So there is a bit of a trade-off. Like most power applications there are hazards. For internal combustion devices fire is a significant hazard, for an electric outboard, the presence of water and medium DC voltage can result in a shock hazard environment. One path is to limit the hazard, and that can only be accomplished with adequately isolated power systems. This includes electrically isolated sealed battery systems and continuing that isolation up to the human user interface (throttle). Moving forward above 60V is a path for another motor, and will be evaluated on the next episode.
As the warm weekend approached, controller wiring commenced and a rough prototype was up and running. I had set up the kelly controls software to work with a 'quick an dirty' 3 wire usb uart adapter cable and set the battery current to a happy 100A and the phase current to a reasonable 120A max. This controller is sensored, so, getting sensor wiring up to the controller, in a relatively short shielded path was quite important.
Battery Options for KLS7240S controller.
For this particular controller + motor setup, I had a few options from my battery arsenal, nominally as the controller will be operating in a constant current mode, and probably not be RPM limited, the battery selection is not as crucial. The controller itself has an operating range between 24 and 72v, so, aiming for high capacity while also having a low voltage is ideal for safety and for going the distance. For the first test I'm running 2x of the 8S LiFePO4 modules, as it provides a reasonable capacity at less than 60V 
TopologyKWHVoltage ChargedVoltage Discharged
13S LiFePO4 module [Prismatic]5.246.839
2x 8S LiFePO4 module [Prismatic]4.457.648
2x 9S LiFePO4 module [Cylindrical] 2.864.854
2x 8s Li-Ion module 1.765.248

An Early test of the Electric Outboard V2
For the first outing of the year there was a proper retreat + outboard testing shindig. Shown is the ~8' Jon boat with a bunch of lake-cruft, including a PID controlled charcoal BBQ, a rotary meat apparatus and an inflatable unicorn.
After transporting everything to a spot to camp out, I went back for the outboard. Note how low the long shaft  outboard sat in the water. I later found that prop positioning, angle and height heavily affect the performance and speed characteristics. It was also apparent that the transom mount (or lack there of) was not even close to being suitable for the amount of force the new outboard could push.
A ratchet strap was added to help counter the outboard torque, but alas, getting to 30% throttle resulting in some fairly harrowing torque.
It was much more peppy and exciting than i had previously encountered. Note that the handle, which was fixed-mounted to the outboard was a bit strenuous to handle. Accelerating hard would launch a bit, and without having control over the angle of attack, the front would launch up a bit.
Here's some early shots of us all zooming about the nearby resivour* (yes electric watercraft are permitted). Note how low the actual outboard sat under the water surface. More to come on fixing that issue.

Notes from the first test
* A better transom mount is required.
During the first test, I relied on the existing, small wooden transom mount. It worked splendidly for a small 12v trolling motor, but became an issue whenever the outboard was pushed to more than ~30% power, as the rear of the boat started to become less structural. A new mount that ties together the back of the rowboat would really make a difference. For the test, the torsional forces were mitigated temporairally by adding a ratchet strap to the center seal area, but  the amount of force applied but it was still rather tenuous, all things considered. Mechanically reinforcing the back and making attachment points for carrying the forward force into the hull is a must, moving forward. 
* Tilt adjust on the transom is a good idea
The actual 'trim' that the outboard had in-water is actually fairly important as it nominally defines how the watercraft wil perform. After the first test I consulted a few colleagues with more time at sea than myself, as it turns out 'trimming' is its own art to an extent. 
* The height of the prop is also fairly important.
This particular outboard is a 'long shaft' style outboard, which is intended for mounting higher up on a watercraft. As my rowboat is incredibly low to the water, this doesn't work out that wonderfully as the two combined result in a lot of hydro-drag. 
*Hear me out, hydrofoil
The results of this first test were curious, mechanically the prop turned, the motor was happy and the electronics stayed under control. The big issue was the outboard being incredibly long, it caused quite a lot of hydro drag being so far underwater. Lets start with a conventional setup, a watercraft that would take a 35hp outboard is generally a bit higher off the water and generally 12-18' long. Lets start with the assumption that this watercrafts transom is 6-8" higher off the water surface than my row boat. Now, lets shift to a 'long body' outboard, which, research suggests is 10" longer than the same outboard model that is not the long-body style. We're now seeing a roughly 16-18" difference in prop height. This is a significant difference in prop height and resulted in a bit of drag. Not all is lost though, 16" is enough to lay in a small hydrofoil under the craft. I'm talking a set of wings to hold the craft out of the water and up in the air. This would significantly reduce the hydro load on the craft while also making proper use of the long body'ed outboard. Its not unheard of to add a hydrofoil to smaller craft, competitive sailing folk do it frequently.  A curiosity for another weekend indeed.
* Maybe Pontoons is a good intermediate solution to twiddling with a hydrofoil?
If the outboard is more suited for a raied craft, maybe raising the existing row boat out of the water and reducing its footprint is feasible. I imagine some ripstop nylon or vinyl sheet may work quite well for this application, as the fabrication would nominally require a long tube and possibly some ratchet strap points to keep everything connected.
* The DC link cabling wasn't appropriate
As this was a test, and I didn't know where the prismatic battery modules would end up living, so I opted for using a longer dc-link cable. This cable was 8 gauge which, at the current that was being consumed, was rather small. As a result under heavy load the controller would buckle as its DC feed was probably dropping fairly hard. Realistically the  battery module ideally lives a short wire run away from the motor controller and uses ~2-4 gauge wiring, and a substantial connector. 
*The controller and cabling need a shroud, the motor needs a coolant fan
While there weren't any significant overheating events, the motor was running quite warm under load. A quick option for providing cooling at the top of the motor is either a better designed impeller, or a proper blower. This could be a simple 3d printed fan attached to the motor shaft, or something off-the-shelf that fits.  The existing impeller for the motor is rather mediocre. Finally as this is not a sensor less controller, grabbing a few watts off a motor phase isn't a terribly bad decision, and gets around having to run separate isolated cabling just to run a fan.  The VRMS on the motor phase should be, worst case, vbatt, peak to peak, and running that through a rectifier and into a proper blower should dramatically increase the cooling capabilities. Another option is to add a water jacket to the motor but that seems fairly overkill. It may allow running higher than rated motor current, but its unclear how much extra power is reasonable. The controller itself may also benefit from forced air cooling.
*Motor Temperature and controller temperature
The motor has an internal thermistor, but i do not utilize it yet. Having a thermal output reading gives a reasonable indication of motor overloading. The controller at present actually allows for a 'boost' mode, There's a peculiar chart of the boost and economy modes, shown (right). This is a little confusing, there are two modes, "Economy" and "boost", the way this is intended to work is if boost mode  is enabled in the controller, selecting it by toggling the BRK_AN(2) line high results in the maximum current being IMAX, when BRK_AN(2) is toggled low, the max current is 60% of IMAX. So, for this to work, the actual max current is set higher than expected, and you operate normally at 60% of that value. Its an interesting setup and could result in a neat 'I need 40% more please' mode. 
I havent wired in reverse yet, I'm a bit anxious about including reverse as at full power its an excellent way to capsize the craft. The controller supports  'half speed in reverse' which is actually impresivley useful in this application. I'm still anxious about enabling it, maybe some extra on board flotation is required in the back of the craft.
It would be great to grab telemetry of DC bus current, Phase current and motor RPM, along with motor temperature. Technically most of this information is sent out the 4 wire TTL uart port of the controller but its not presently documented in the manual. Kelly controls actually sells a blue tooth module that can connect to this along with an APK for android, but I have not yet tried it out / verified it supports data logging. One reason having motor rpm available would be to indicate what band the motor is operating in, is it hovering in the 2k rpm region at full current, or is it approaching 5k rpm? If I'm only hitting half of the target rpm at full current this would be a great indicator that the motor could benefit from a belt reduction, resulting in the motor operating at a higher rpm and transferring more power to the prop.
* Error Indication
Right now the Kelly Controller outputs blink codes to indicate different error modes. At present those led indicators are located in a bit of a precarious location. Either being able to read these over the coms link, or, remot-ing the indicators would be useful for in-field debugging.
* Waterproof throttle
One of the parts that i was a bit precarious about was the simple hall-throttle i had been using for throttle. They are notoriously bad when it comes to moisture. Oddly enough 'waterproof scooter throttle' isnt really an off the shelf item yet. I imagine the throttle out of a zero-electric motorcycle probably actually works in the rain but at the moment the concept of 'the throttle got wet and the boat decided to apply max power' is a bit of an issue. There are a few solutions, conformal coating spray applied tothe hall effect sensor, finding an actual waterproof throttle, or, simply using a set of well tested waterproof pushbuttons to simulate different throttle settings. possibly a sealed multi position switch and a forward pushbutton? It would be neat to actually have a bell call lever for throttle set and some type of dead mans switch to prevent 'runaway boat' syndrome.
* A shroud for the mechanicals
Finally, adding a shroud around the top to clean up the look of the outboard would be great for also hiding the cabling and any exposed rotating parts. It would be pretty excellent to go for some ~60's era spaceman-spiff look,
* An Emergency Stop
The correct wiring for this motor controller uses a contactor to enable / disable the drive, which, for all purposes is a good idea. During this test i wired the battery bus directly to the input for simplicity but having a contactor and a pre-charge is a really good idea going forward.
* Detecting leakage current
One interesting mechanism to limit and detect to the hazards of medium voltages in a watercraft is to having indication for hull to battery leakage. I imagine if there's any voltage present between hull and Batt +, its a good idea to stop and determine why or what is leaking. This may be a DC leakage path, or high frequency AC coupled through to the hull.  I hesitate to use a ground fault indicator as, well, this is a DC low voltage application but it may be a good idea to investigate what is available in that realm. I imagine there's 48V DC widgets on swanky yachts, or sail craft, so there may be associated safety hardware. Finally using a large system fuse, with an indicator would be a great last step forward, having a zener-resistor led setup to display 'your fuse is blown' would be quite great. DC circuit breakers at that power level are a bit expensive or huge, most reasonable sized ones end around 50V, at 50A DC.

Solid part files

(There's other photos in the photo gallery)
Concluding Remarks:
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Stay safe when working with electrons in aqueous environments. Also wear sunscreen, I'm not responsible for your newly aquired farmers tan : ]

Rensselaer Polytechnic Institute 
Electrical & Electrical Power