We purchased our 1973 Catalina 27 as a relaxing weekend getaway. We got a great deal on it because the atomic-4 engine was not working and we were told it hadn't in several years. The sailboat had an 8 hp outboard on the back, which wasn't the most reliable when it was cold or running at really slow speeds. It seemed like when you needed it the most; it would stall out going in and out of the marina. Reaching over the transom and working the tiller at the same time was also a little difficult.
After doing some research online and at the boat show, we found the cost to replace or repair the inboard engine to be quite expensive, so we decided to do-it-ourselves and convert our sailboat to an electric powered sailboat. We felt that electric power would work great in a sailboat application because you usually only use the motor to get in and out of the Marina.

The Birth of our Electric Motor
The first step in our conversion was deciding what we needed to complete the project by creating a bill of materials (see below). After doing some research and planning, we decided to go with the Mars Electric Brushless Motor; we chose this motor because it is very affordable and powerful. This motor is capable of producing up to 15 HP (6 HP continuous). It also has a stationary three-phase motor winding, with a very simple permanent magnet rotor. The benefit of this is that there are no brushes to wear out, and there is no ignition source for any on-board gas appliances. However, with a brushless motor, you can't just hook them up to DC and make them spin, because they require a three-phase controller. We chose a 250 amp Sevcon PMAC, regen controller. With a regenerative controller, as the prop spins during a sail, you are recharging your batteries. Once we had decided on this combination of Motor and controller, it was time to put together the rest of the sailboat motor kit. Our motor kit includes a Mars Brushless Motor with the Controller which is a programmable Sevcon 250Amp w/ regen, a throttle, which is a PB-6 pot box, this box converts a mechanical cable to an electrical signal for the controller. We also got a Fwd/Neutral/Rev toggle switch, a keyless on/off switch, and a contactor which is a battery disconnect operated by controller. The last item in our kit is a buss fuse and of course welding cable to bring it all together. We assembled our own kit and did all of our own wiring. However, having done this already, if we did it again we would buy just the complete kit with instructions rather than piece it all together we didn't save any money or time. This complete kit listed above is available online at various stores.

So now that we had our motor kit, we needed to figure out a way to mount it. After searching on the Internet for the best way people have done it in the past, we could not find anything suitable. As owners of a complete machine shop, we decided to make our own motor mount system. Our motor mount system consists an adjustable motor mount frame and plates assembled with the appropriate sized thrust and support bearings, a stainless steel drive shaft with a stainless shaft coupling, which connects prop shaft to the drive shaft. A set of 2 to 1 reduction pulleys, which improves efficiency and provides proper torque, cooling and prevents cavitation. Our mount kit also includes the drive belt, the controller mounting plate, which is a heat sink and a Lexan belt guard for safety.

Next thing we needed was the batteries, so we purchased four of the 1st Optima Troll fury batteries with a total of 48 volts. These batteries are highly rated for this type of application because they are designed for the rigorous demands of professional and sport fishermen, the Optima battery offers long reserve time, physical durability and a fast recharge rate, we found their prices to be excellent and this company offered free shipping.
After purchasing the batteries, the next thing we needed was a good charger; we decided to go with the Four-bank Pro SE charger from Dual Pro. They offer reconditioned units for a great price on their website.

Prior to bringing our motor down to the boat, we assembled the motor to the frame, clamped it to the workbench and connected the batteries to test it. Now that we had a complete running electric motor, the next step was to prepare our sailboat engine room for our new electric motor.

Removing the Engine - We removed all of the engine hoses, and cables as well as the 4 bolts to the engine mounts. (We did need to cut one bolt off which was under the water pump because it was rusted) Next, we screwed in eyebolts into the head of the engine in the place of 4 of the head bolts, to assist the lifting process. (This helped to prevent the engine from tipping when being lifted.) We then sailed our boat over to the boat yard and they lifted the engine out with a crane in just a few minutes. We do not recommend attempting to remove your own engine without professional help. The cost for this lift was only $150 at our local boat yard. Much less than the cost of visits to the Chiropractor!

Cleaning and preparing the Engine room for our new electric motor.

Once the engine was removed, we removed the old hoses and old gas tank. (This was really helpful in making extra space) We kept the throttle cable in place for the new electric motor. Next, we cleaned the engine room with a marine grade detergent and painted it with white bilge paint. The engine room was now ready for our new Marine Electric drive.

Installing the new motor was much easier than we expected, first we needed to remove the old prop shaft coupling and replace it the stainless coupling for our drive shaft. The old atomic 4 coupling was rusted to the prop-shaft and required a three-jaw puller to separate it form the shaft. The puller was purchased at an Auto parts store for $30.

Next with the adjustable frame we just slid in the assembled motor lined it up with the prop shaft, adjusted the pitch and side angle just a bit and tightened the coupling and mount bracket screws.

Once we had the screws tightened we spun the pulley to make sure there was no binding in the shaft. If there was we would have readjusted the angle or pitch, but it wasn't necessary, we got it right the first time. Next, we drilled four holes into the engine bed and screwed in four large lag screws to secure the motor.

We installed the four batteries and secured them down in battery boxes, where the old gas tank use to be.

Next we mounted the charger to the bulkhead, wired the batteries to the motor, connected the throttle and on/off switches and put them on the operator panel.

Now our electric sailboat is enjoying the quiet clean virtually maintenance free motor.

Learn more on the web at Electric-Sailboat