just saw a neat story on youtube about a guy in seattle that had the diesel removed from his 27' catalina and replaced with an electric inboard. short version is that it would give him about 1.5 hours at 5knts, around 5 hours at 4.5knts without a charge. the installer told him that he would recharge his batteries to full power if he sailed at 3-4knts for around 8 hours because of the system set up to send energy from the spinning prop back into the batteries.
looking online i see there are alot of products out there for inboard / outboard electric motors. has anyone looked into this? i think i'd sure consider it on a daysailer / inland cruiser. so many of the real frustrating engine issues would be eliminated. (i think) i'm no expert but the tech seems to be really interesting
obviously batteries are the big weight / cost issue but they are changing so fast now that it makes it possible
Yes, you can use electric to power small craft, but the same issues always apply; range, weight, recharge time and speed. For example, the Catalina 27 has a displacement speed of about 7 knots, so his full speed under electric is about 30% less than his theoretical hull speed. The Catalina 27 is well shaped, so it can do better than it's normal hull speed, so actually even less under electric. I seriously doubt a spinning prop under sail can charge a battery bank in 8 hours under sail alone. A plug into a wall charger would take the better part of a day and the self generation portion of a dragged prop, is way less efficient than a dedicated 120 or 240 VDC charger.
Most of the electric systems are at a serious weight disadvantage to gas, particularly if air cooled. Next up are costs and complexities of the systems, which are well over (still, but coming down slowly) more conventional propulsion means. Then there's the range thing, which is always a bummer once you take a look at it. More range, means more battery weight, which slows you down, even with lithium ion.
I use electric on my ketch, which is 23', but for me it's practical, as I don't need to use it much. I need to get away from the slip for a few hundred yards and I'm in free, open water to hoist. I'm never very far from shore and usually within an hour travel time of the slip. I run two group 24's, which get maintenance charged when I drag her home.
Lastly, costs are still much higher than equivalent outboards or small inboards. Look at the price for the latest and hottest electric 3 - 5 HP and compare them to a 3 - 5 HP outboard. Now add a few extra batteries to the list, so you have similar range and well it's a deal breaker, pretty quick. Things are changing and some can use electric if they don't need much range, but as a stand alone system, there's a lot to consider.
I plan to manage with electric, but I don't need the engine even to get out of the home marina.
It is only for beaching or docking in difficult/crowded environments or dead calm nights to get ashore. And manouvering in the locks maybe.
Also I have the petrol driven generator should I need more than two hours range
. Solar panels should be enough in normal use.
Sorry I didn't mention they had more speed just depleates the batteries faster.
I'm sure this area will keep improving, also looked at propane powered outboards
lots of new ideas on the horizon
A propane "kit" can be installed on most outboards and inboards now. It's not difficult if you're handy with a wrench.
i keep seeing more and more boats that have made this switch, it's interesting to see. found a number on youtube that are full time cruisers that have gone electric.
There'll always be folks that just toss up their hands and say "I don't care what it costs" . . . and bite the bullet anyway. Yes, electric is coming along, but it's still not here yet, unless you don't need much range and can afford the weight of a bank of batteries.
In larger applications, particularly ones that have a bigger percentage of propulsion needs to house needs (refrigeration, lighting, battery charging, electronics, etc.), it's more viable, because you're running a big generator to power the chargers, compressors and the electric propulsion too. This crossover threshold is about 50% propulsion/house needs, to make it a reasonable option. These are commonly called diesel/electric setups usually with a "pod" style of drive. I've seen some smaller setups with gas generators that work, but are less economical.
One I saw a few years ago, was interesting. It used a small gas engine to drive a big alternator (150 amp) which was used to charge two big batteries (80 pounds each). One battery was always kept in reserve (getting charged), while the other was being used to drive the boat. This setup would keep the reserve battery fairly fresh, to use as the "get home" battery, once the battery in use, drew down to about 50% charge. He also had some small PV panels, to maintain charge once the boat was parked, but they were not enough to keep up with usage. He had about 3 1/2 - 4 hours range with this setup, but he was running pretty slow at the end of this period.
Again, once you count up the costs with controllers, switching, inverters, batteries, etc. the weight and range issues still come to haunt the performance and time underway aspects of the setup. If like me and Timo, you find you don't need much range and the weight can be kept low because of the battery count, it works. If you need more than 2 hours of run time, things get expensive quickly, because you need more batteries, higher voltages (36 - 48 VDC) and costly bits and pieces.
Lastly, prop selection is an issue. Trolling motor props are designed to run at about 3 MPH, which is pretty darn slow for most. To get more speed, you need bigger and different pitched props. Many are using model aircraft props, mixing and matching to suit their needs, though this is a "hunt and peck" approuch it does work, once you're narrowed down the selection. I have a motor I've been playing with last summer and it's a really nice brushless DC unit with about 2 HP. It works great, but sucks the life out of a group 24 battery (most common automotive size) in less than an hour, at which time the battery is surprisingly hot. It can push the ketch to nearly displacement speed (7 MPH), but it's hard on the battery. Fortunately, I only need a few minutes of run time, under normal operations, so it works for me.
It's up to you, but you'll have to play around with several different things to iron out the details. Alternatively, you could just buy an electric outboard. These details are worked out with these puppies, but the pricing will make you gulp.