First of all, all motors will be of the "Short Shaft" variety. The shaft measures approximately 22 inches from the top of the clamp to the center of the propeller or approximately 15 inches from the top of the clamp to the waterline.
Depending on the geographical area you live and the size of your catamaran will determine how much horsepower you will need. If you are sailing in freshwater lakes with no currents, you can get by with as little horsepower as possible.
If you are sailing near the Atlantic or Pacific Coast or in an area that has tidal currents, you need a larger motor than the 1.2 HP variety. The motors in the 2.5 HP range are sufficient for the 18 foot to 21 foot catamarans that have around 12"-15" of freeboard giving you sufficient space to make installation adjustments. The Hobie 14 & 17 and Prindle 15 & 16 only allow for the very minimum horsepower and weight. I also recommend an aluminum 3 bladed propeller for more thrust against currents and tides. Sometimes the outboards mentioned below come stock with a plastic prop but offer an after market aluminum prop. Get the aluminum prop.
The more readily available motors are from Johnson, Evinrude (Etec), Nissan, Mercury, Tohatsu, Yamaha, and Honda. They all make a 2.5 HP version ranging in weight from 25-30 pounds. They also vary in price. These are all water cooled and are just a little quieter. Another company that offer both 2 cycle and 4 stroke is
Another great alternative power source is a new and very innovative product called Torqeedo. This is an electric outboard weighing less than 30 pounds and is absolutely silent, NO NOISE!
With the Torqeedo, you never have to worry about spray in the carberator when sailing
(no motor cover).
You do not have to take an extra spark plug in case of fouling and no fuel to spill.
The other incredible feature is they are very efficient. Take a moment and visit their web site:
The Torqeedo that works on our brackets are the 503 and 1003.
FOR GAS OUTBOARDS CONSIDER THE FOLLOWING TIPS BELOW:
* Always sail with an acrylic canvas cover over the power head of the outboard to protect it from spray.
* Always take an extra spark plug and spark plug wrench with you. The spark plug is basically a resistor and with moisture, can short out.
* If you are going on any long trip, consider taking along extra fuel. A quart oil container can take enough pre-mix for maybe another 2 hours running time. These engines sips the fuel. Also, you will find you will go just as fast at half throttle as full throttle, the only difference is you're using more fuel for the same speed, so drop it back to half throttle and save fuel.
* If you are flying a hull and should go over, jump off the high side to prevent the boat from turning turtle. When the boat is on its side the motor is actually further out of the water than when straight up. But if you should turn turtle, get to shore, drain the gas tank, carberator, and combustion chamber, refill with new fuel and run the engine to dry out the motor as soon as possible. If you have a solid state ignition like I recommended, you'll be fine.
Cost vs Value