Snow Lily, Tartan 34C powered by Electroprop Mariner – Electroprop’s Top Efficiency Driveline
Snow Lily is a 1969 Tartan 34C which I purchased for next to nothing when the boat was a week away from the scrapyard. Tim Lackey of Lackey Sailing, LLC in Whitefield, Maine took on the project for me of a total and complete restoration. every inch of the boat was redone over a year and a half of continuous hard work. Tim is a traditionalist and was skeptical of electric propulsion, but willing to install it if I so chose.
I considered the issue for many months and came to the conclusion that a diesel repower would be best, but found I just could not close the deal on that decision. So after months of deciding diesel but not able to simply tell Tim to go diesel I realized I really, really wanted to try electric. I have numerous internal combustion engines from an old pickup, to an old small airplane to an old snow cat and I just couldn’t bring myself to add another ICE to my maintenance workload. Also, the few cruising boats I’ve sailed on all had a slight whiff of gas or diesel odor and the though of installing one of these in my main cabin living space just repelled me. So electric was my decision given to a reluctant Tim Lackey. He did say it would greatly simplify the repowering eliminating cooling water intake, fuel tank plumbing, exhaust and finding room for a new diesel to replace the old Atomic 4. So in that respect Tim was pleased, but he warned me that motoring range is the compromise.
During this time talking with a few folks in the electric motor business I settled on James Lambden to be my partner on this. His experience and understanding of this somewhat new technology and his ability to communicate what was important and why sold me. Every minute of working with James has been good and I can count on him to follow through and support me during this repower.
Early on I realized the size and weight of lead acid batteries would be a big disadvantage; so if I could not afford lithium ion I may have to reconsider electric. The Tartan 34C is a classic design and not as beamy or roomy inside as more modern boats and finding the right location for the cells was an issue. Tim Lackey finally settled on the same place where the 26 gallon gas tank was located, below the cockpit just aft of the rear bulkhead. It is on a slight slope, but the battery manufacturer assured me this was not a concern,
We were planning on ordering sixteen 300 amp hour cells from China when James called me and said he could pick up a set of new 260 amp hour cells in LA immediately and at a substantial discount. Reviewing my energy budget I decided this would work and so we went for the 260 AH cells. Of the several reputable brands, I chose Winston for my boat; there may be equal or better quality cells available, but the Winston chemistry specified -45C as the low temperature range. Snow Lily is a northern boat on Lake Superior, and during winters on the hard the temperatures can easily reach to -30C and even -40C is not unheard of.
Security for the batteries was very important and James Lambden fabricated two boxes, eight cells each, which both clamped the cells and then were bolted and strapped down to a battery foundation built up by Tim Lackey. A thick piece of clear plastic covers the cells to prevent accidental contact.
The original Atomic 4 motor foundation was a mess like most everything else on this used up boat. Tim Lackey built up a new foundation precisely aligned with the new prop shaft. So in the photos you see a directly bolted motor- we did not need James’s very nifty motor support pan. Tim also extended the shaft support to aft to provide room for the prop recommended by James.
So how does it work? Remember as of this writing I only have very limited experience. In late July we did a full day of motoring sea trials in Maine in Booth Bay. Then in mid August I took delivery of the Snow Lily at her new home on Madeline Island. By the end of the season, late September, I had only sailed or motored the boat 7 days.
I just love it ! I couldn’t be happier with my decision to go electric. The motor is wonderful and trivially easy to use. Maneuvering in a tight marina to my slip couldn’t be easier; go full forward to full reverse thrust if needed without a second thought. The controller takes care of it. The slow speed control especially is great for docking. Being new to larger cruising boats I have a lot to learn on boat handling in tight quarters, but having the electric motor is making this far easier for me.
In estimating the needed performance James programmed the controller to limit the RPMs to 2000 and this seems just about right. If needed, 2000 RPM will drive the boat at 5.5 knots with about 3.7kW. Note, this motor is 5kW continuous. To reach hull speed of 6.7 knots we’d need to raise the limit a little to about 2300 RPM, but I’m not convinced I want to do this. The power needed for the extra knot is substantial and like most others I have found a boat speed of 3 to 4 knots is the sweet spot where reasonable speed while preserving battery energy is located.
In using the boat this past late summer and fall I made numerous instantaneous readings of speed, amps and volts. These then I plotted in various ways and I’m attaching these plots. This was not any kind of measured scientific testing, simply recording readings when convenient. Lots of things like wind, waves and current were not accounted for. I figure if I keep adding points to these graphs the performance characteristics will be pretty well defined. Right now I believe James Lambden has designed a great motor, gear ratio and prop combination for my boat.
Snow Lily a 1969 Tartan 34C