After careful consideration and some field testing (lake testing?) I've decided to keep using an electric motor for auxiliary sailboat power. I'm not using one of those specialty high end electric outboards either. A humble 55 lb thrust electric trolling motor works just fine.
Last summer all we used on the sailboat was an electric motor. When the gas outboard broke it was a cheap and easy solution. After all, it is a sailboat. Expectations were low. If the electric motor could push us out to where we could raise the sails that'd be enough.
Performance was better than expected. My Oday 19 isn't all that big a boat, but it's not a dinghy either. Wide open the trolling motor could push the boat along at a steady 3 knots. Not only that it could keep us moving at that speed for hours. At the end of the day when the wind dies that's good to know.
Hull speed is rated at 5.5 knots. The 6 hp gas motor moved the boat at hull speed, so there was definitely some loss. The 1.5 knot difference doesn't sound like much -until trying to get into port against a 4 knot tidal current. It is a consideration as that's actually happened to us. We crawled into harbor at a bit over a knot.
Liquid fuels pack a lot of punch. Gas is available just about everywhere. It's a mature, well developed technology. It's also explosive, toxic, non-renewable, and just plain stinky. Gas outboards, especially my old one, are loud. Some of the newer ones are much cleaner and quieter, but they still burn gas.
Propane outboards tempted me. They burn cleaner, but are just as loud as gasoline engines and propane has explosion hazards of its own. Mechanically the only real difference between the two is the carburetor. Propane is often available around marinas because many boats use it for cooking, but it's not as common nor as easy as pulling up to the gas pumps.
How about recharging the trolling motor battery? All last summer the boat's solar panel kept the battery topped off. It was nice not to schlep gas cans down the trail to the boat. Also very nice to not worry about spilling gasoline into the water. Marine patrol takes that sort of thing very seriously -as well they should. In the past my lovely wife and I stayed in marinas part of the time. Most of them had electric power right on the dock so charging a battery from shore power is easy.
The motor worked on fine on my small lake, but what about bigger trips? We won't be able to power our way out of trouble if the wind dies. Fair enough, but if there's no wind the electric motor can push us along well enough. On a long trip brining along a spare battery or two would be prudent. What about those strong tidal currents? That's where careful attention to tides and weather forecasts take on greater importance. Good ground tackle is also more important. Anchoring and waiting for better conditions might be necessary.
One big advantage my lovely wife and I have is our lack of schedule. We can sit out poor conditions in a well stocked boat. If it takes an extra day or two to get where we want to go it's no big deal.
Having made the decision to stick with electric, I'm going to make some boat modifications. The big one will be moving the main batter to the gas tank locker. That will help with boat balance and free up some space in the cargo hold. Wires will have to be rerouted, but it will be worth it in the long run.
The Oday 19 is about at the upper limit for this sort of auxiliary power scheme. If and when we get a bigger boat I'll have to rethink the whole power thing all over again. Then again, we are talking sailboats here. There are many people who sail all over the world in good sized boats without any auxiliary power at all. Some boats even use a yuloh, which is a long sculling oar. That's a discussion for another day.