By Sam Masoudi

When we purchased our Selene 47 in December 2015, we were aware it did not have get-home system. We decide if we needed it, we could install it later. Although our Cummins QSL9 had been extremely reliable, my thoughts often returned to how to stay safe while underway in the event we lose main propulsion.

About 4 years ago, we decided it was time to look seriously into our options. We soon discovered that a generator PTO driven mechanism was not a viable option, as our 8KW Northern Lights generator is too small for a PTO application and Northern Lights no longer offered the modification kit for it. I discovered another Selene 47, Jean Marie, had installed an external electric motor for auxiliary propulsion. I contacted Rick Panowicz and he was very generous in sharing his positive experience, boat performance and installation information. A season or two passed, a few more projects, and once again we returned to the topic in the fall of 2021.

We were more focused on pursuing an electric motor and I found many examples of installs, primarily on sailboats. Most of these examples were total replacement of the diesel engine with an electric motor either direct or via a chain/belt connection to the propeller shaft. We decided to further explore the possibility of an internal electric motor installation with a coupling to the prop shaft. This is what some in industry call a “Hybrid Diesel Electric Parallel” application.

I made a simple sketch of what I was looking for (Figure 1) and started contacting electric motor system suppliers. One of these companies was Electric Yacht in Golden Valley Minnesota which followed up with a number of positive communications. Scott McMillan the President/CTO of Electric Yacht expressed interest, as his company had done a similar application on a Nordhavn 43 a few years earlier. I was impressed with Electric Yacht’s can-do attitude and became more confident that the installation could be successfully accomplished. I provided our boat’s Propeller and shaft diameter, RPM vs Speed Through Water (STW) characteristic and my target minimum STW speed of 4.0 knots. Scott recommended a 20HP system kit and also volunteered to procure and install the 24V clutch on the motor assembly. We agreed on a way forward on December 26 of 2021.

FIgure 1. The System Concept

System Architecture & Installation

The QuietTorque 20 HP Electric Motor is a 48V plug-and-play system and comprised of the following components:

2x 10 HP electric motor assembly	Motor controllers
Relays	Battery switch and fuse
Motor mounts	Throttle
Motor monitor	Key Switch

A 24V Pitts electric clutch was also incorporated with the motor assembly.

Although Electric Yacht provides battery and chargers, I decided to source those and a few other parts separately:

2 x 48V 100 AH EG4 LiFePo4 racks	2 x 48V 50A battery chargers
9.5” diameter timing belt pulley with 2” belt width	Victron battery monitor & shunt
Quick disconnect bushing for a 2 ½ propeller shaft	Assortment of cables and lugs
2 x H series timing belts (one as spare)

FIgure 2. The electric motor arrived!

The Motor assembly arrived in mid-March 2022 (Figure 2). Due to the space available in the engine room, the electric motor assembly had to be installed on the starboard side above the prop shaft near the back of the engine room. One side of the motor assembly rests on the engine starboard stringer, but I had to build a platform for the port side.

I fiber glassed a flat surface inside the engine bed below the prop shaft (Figure 3). then made two teak offset platforms to sit on the fiberglass platform and perpendicular to inside surface of the starboard stringer (Figures 4 & 5). I also found adequate space at the back of the engine room to install Lithium battery racks, chargers, cable buss, fuse, solenoids and main battery switch (Figure 6 & 7). We then hauled out and pushed back the prop shaft a few inches and slid in the 9.5” diameter pulley and H type belts (Figure 8).

FIgure 3. The port floor platform

FIgure 4. Prototype port offsets

We then routed the motor control wires from engine room to pilothouse and installed motor monitor, throttle and the key switch (Figure 9). After measuring, cutting, and crimping a number of cables the system was ready to test.

Operation

Our get-home system is envisioned to be used in the event that the diesel propulsion is disabled, but the prop shaft is able to freely rotate. As long as the electric motor key is switched off the 24V clutch is disengaged and prop shaft does not transfer torque to the electric motor. I should add the system is capable of power generation (Diesel engine running electric motor), but this is a totally separate discussion.

FIgure 5. Port platform installed

FIgure 6. Lithium battery racks

The clutch is engaged when the electric motor key switched is turned to ON position, then the electric motor is ready to transfer torque to prop shaft via the belt. Advancing the throttle control in either forward or reverse causes the motor to spin the prop shaft in the appropriate direction to move the boat.

The initial test at the dock was successful in rotating the prop shaft and setting the throttle responsiveness. We delayed the in-motion test until we attended the 2022 Rendezvous in Roche Harbor. Before leaving the area, we attempted a full system test and quickly found that the belt tension was grossly inadequate and motor torque was not being transferred to the prop shaft due to belt slippage. I had initially set the belt tension, with much difficulty, using rod clamps to push the motor assembly to starboard before tightening the mount bolts. In addition, establishing a parallel line between center of the motor assembly and the prop shaft while tensioning the belt proved to be a tedious task.

FIgure 7. Motor relays and switch

Back in Everett and in consultation with Electric Yacht, I realized we needed a better system to a) tension the belt and b) more rigidly secure the motor mounts to prevent the potential of flexing. I also realized I needed help with the tensioning system and was extremely fortunate to meet Mike Greenleaf owner of the Everett Sound Machine Works. After describing the project, the belt tensioning difficulty and the space limitation, Mike suggested a “Pull” concept and manufactured a pair of Aluminum brackets (Figure 10 & 11). The brackets were linked to the unit’s starboard mounts via threaded rods. By tensioning each threaded rod, the unit was easily pulled to the starboard. This system not only helped with the belt tensioning, but as importantly allowed micro adjustments of the front and aft mounts to keep the unit parallel to prop shaft.

FIgure 8. Motor with drive belt installed

FIgure 9. Monitor, throttle, and key switch

With successive and incremental belt tensioning, we were finally able to achieve and sustain 4.5 kts STW last summer. Needless to say, this was extremely satisfying. At that time, I realized that the system had more capability, but decided not to push the throttle further, as we were exploring in Desolation Sound and the Broughton far from our home base.

We are planning to examine further the limit of the system this summer. Of course, increased boat speed means a shorter range. In order to extend the range beyond the current battery capacity, we’ll need to turn on the generator and utilize the 48V chargers. Although we have not explored the full capability of the system, I expect a 2-3 hours range at 4 kts. Clearly, the range can be further increased by adding to our battery capacity and/or additional battery chargers.

FIgure 10. The new belt tensioning brackets

FIgure 11. New tensioning brackets installed

Although space is not unlimited, with a few adjustments, I can find additional space. Currently, I am more than happy with the 2+ hours range, as our primary goal is to safely avoid an emergency situation, move to a suitable location, secure the boat and determine the cause of the diesel engine failure and hopefully address it.

Conclusion

The marine electric motor industry and battery technology is expanding and growing fast. Many sailboat owners and manufacturers have switched totally from diesel propulsion to electric. This is still a new phenomenon for the trawler market and replacing the diesel engines with electric motors is not likely to happen any time soon. However, using an electric motor as a get-home or potentially as a generator is a realistic option not withstanding space limitation. We are pleased with the electric get-home motor as an option. We may never have to use it, but it is comforting to know it is there if needed.

After further evaluation this summer, I have a few additional improvement projects for this system:

• Create a belt idler mechanism for better wrapping of the belt around motor pulley

• Determine a safe method to combine electric motor 48V lithium batteries to the house 24V lithium batteries

• Explore power generation of the electric motor system

We will be at the 2023 Selene Rendezvous in Roche Harbor in April. Please feel free to let me know if there are any questions