Sigi - Case History - Electric and Hybrid Propulsion
Case History

Sigi – Case History

Posted On January 30, 2017 at 11:05 am by / No Comments

Sigi - Case History - Electric and Hybrid Propulsion When I took possession of my 20 foot wood sailboat, Sigi, the vintage Kenmare Sea Twin (aka Atomic 2) inboard had been removed from the boat. I suspect that my uncle, the designer and owner, was going to fit it with an alternator and electric starter (instead he bought a Flicka). My aunt told me that the motor was temperamental and a hassle to rope start. Fuel was supplied by two, three gallon portable tanks that stowed beneath the cockpit seats. I was instructed not to fill the tanks more than half full; otherwise, the tanks would spill fuel when the boat heeled. The throttle and linkage assembly was mounted on the cockpit sole.

I was not comfortable with reinstalling the Kenmare. The gas engine made me anxious. It also requires leaded gas and replacement parts are not readily available. So, I made a decision to replace it with a new diesel. However, after much research, discussion and measuring, I could not find a engine that would fit in Sigi’s shallow engine compartment. The reps from the manufactures were all extremely helpful but the new 10HP diesels were all just too tall. I’m told that we have EPA to thank for that. Having ruled out a new diesel, I searched for an older, rebuilt diesel that might work. Yanmar and BMW engines came close; but, both needed greater clearance between the keelson and the center of the shaft than Sigi’s three inches.

I had stumbled upon (click here for further information) during all of this and emailed Scott, the owner, with my conundrum. Of the three engine sizes offered, he thought the smallest might work. I did my due diligence and arranged to meet with Scott at the Annapolis show. By then I had made my mind up to go with their 100DBL electric inboard.

I did have to make a few modifications to the engine compartment. The existing motor mounts were removed and one of the floor timbers had to be moved about four inches aft. (I had to remove the existing floor timber in pieces and fabricate a replacement from white oak.) Otherwise, the engine install was clean and simple. The electric power plant weighs 54 pounds. I chose four 12V AGM Batteries as the power source. Two each are mounted on a low shelf inside existing port and starboard cabinets just inside the companionway about amidships. The batteries are connected in series to provide the 48 volts to power the engine. The batteries weigh 50 pounds each and should push the boat along at hull speed all afternoon, more than adequate for my purposes. After all, Sigi is not much more than a day sailor and will be under sail 98% of the time (I hope).

I purchased a 48 volt, 15 amp charger and mounted it in the aft, cockpit compartment. The electric throttle assembly,
ammeter and the charger shore power inlet are all mounted on the hatch to the compartment.
Sigi did not have an electrical system. I plan on installing a 48V – 12V converter to power an electric bilge pump and any other accessories that I might deem needed.

That about covers it. I know that there are arguments for gas/diesel propulsion and I know what those arguments are. Most of those who make them must never have run out of gas nor had an engine fail at sea. For my part, I am really happy with the decision to go electric. It’s clean, it’s quiet and the power is instantaneous.
Installation was a snap and it runs like a charm.

Howard Thorkilson

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