You’ll know if you’ve been reading along, following our travels, that we converted from a small diesel to an electric motor before we began our trip. As we’ve described our journey we’ve talked a lot about our struggles with currents and their effect on our motor and batteries.
It’s time to confess: we were a large part of the problem. It all began when we ordered the motor.
It started when we sent the weight of the boat to Scott at Electric Yacht. We should have sent the weight of the boat fully laden (of course, that’s always more than you think on a cruising boat). Instead, we sent the weight of the boat empty. More weight creates more work for the motor and affects the gear ratios that work best. So when Scott set the engine up using our information the gearing was wrong.
The gearing makes the motor drive the prop at the right speed to move the boat efficiently – the engine turns faster than the prop, gearing reduces the speed at which the prop turns in relation to the engine. In our case there wasn’t enough reduction in the gearing to deal with the difference in weight. And that meant that the motor couldn’t turn quickly enough to perform at its best.
This also affected the cooling of the motor. The right ratio between engine and prop will make the motor turn in the range that’s most efficient for cooling. If the gearing meant that the motor couldn’t turn fast enough then the fan couldn’t give us optimum cooling.
And then there was the change between what we were planning to do when we ordered the motor and what we ended up doing. We thought we were going to be sailing up and down the American east coast, on the ocean, going into and out of inlets when we needed shelter or access to supplies, maybe doing some between-island hops if the opportunity arose.
We routinely wait for a suitable tide and current to enter or leave an inlet. If we had done what we originally planned currents would not have had the same impact. So we asked for the motor to be set to run at a continuous 20 amp draw, which we knew would get us in and out of the longest inlet we would use.
But as we all know, life changes and plans with it. Getting to Toronto became a priority, and going up the St. Lawrence a way to do it. Even after we had decided to sail up the St. Lawrence we weren’t sure, until we were there, how much extra current draw we were going to need to overcome the currents against us. It was a chance we decided to take.
That was how we found ourselves in currents on the St. Lawrence where we ended up regularly drawing 45 amps instead of 20. In the most challenging situations we used 55 amps to get the power we needed, and the motor overheated. Which would not have happened if it had been set up differently.
Scott did encourage us to test the system wide open and at its limits when we were first using the motor, and we should have. At the time we didn’t have an efficient way to recharge our batteries, so we hesitated. Which meant that we didn’t fully test the motor and current draw on the batteries until we were underway. And then we really tested them!
We’ve learned a lot as we travelled. And Scott has been there to answer our questions along the way. Now that we know what we know we’ll get the gearing changed over the winter, and use this summer to test the new setup (and that’s a great excuse for just spending time out on the water, though we do prefer using our sails).
And we should mention the things we really like about our motor: clean, quiet, simple controls, lots of torque, low maintenance, very responsive in the conditions we had originally envisioned… And no diesel smoke. With the other engine we had rather a lot of that.
Written by Margaret Mair
Photo by Richard Mair