Recognizing this thread is old times two.... We use a Motorguide 40# VariMax troller on our SJ21 (which if you put it on a truck scales, actually weighs more like 1500# empty.) This saltwater motor has digital variable speed, rather than the usual rheostatic control; so you can expect up to double the run time at partial throttle. It pushes the boat with full gear and two people at 3.2kts, but it's not driving into any headwind above 18kts (we know that from experience
). 40# of thrust is pretty close to 1 hp -- good for maneuvering in decent conditions, but no more. Very much an auxilliary engine.
1. Quiet. So quiet you have peer over the transom to make sure it is running.
2. Weight. Easy to lift on and off the mount (which helps w/ security, too). The SJ21 can tolerate weight in its bow but it HATES weight on the transom. It will squat. The trolling motor weighs 18lbs, compared to over 40lbs for a 2.5 hp 4-stroke with long shaft. Of course, the group27 battery weighs another 60 lbs, but it lives right beside the keel box in the center of the boat and actually adds righting moment.
3. 360 degrees of rotation, slender on the transom, doesn't obstruct cleats or interfere with the rudder.
4. No worries about carburetor gumming, ethanol, impellers, or storing gasoline on the boat. I HATE gasoline on a boat.
5. Trollers are intended for steady, low-speed propulsion, so their RPM range and propeller designs are a good match for sailboats.
6. Price. Digital saltwater troller, big battery, and all fittings cost less than half what a Mercury 2.5hp would.
1. Not much thrust, unless you buy a Torqueedo.
2. Never sure about battery capacity. While overall maintenance is lower on the troller than on a gas outboard, you must watch water levels, terminal corrosion, and replace batteries occasionally.
3. Requires big wires and big amps, which does add a fire hazard. Not as bad as gasoline, but real nonetheless.
4. Our particular motor model has some quirks. When run for a long time on hot days, the urethane-potted variable speed control may overheat; the motor will run at half-speed, or not at all, to prevent melting. Motorguide assures me this is not a design flaw
but a design feature
. I feel better about that.:/ It also, under these same conditions, may continue to run at low speed even when the tiller control is positively clicked off.
Motorguide at first claimed they'd never heard of this phenomenon; when I pointed to numerous internet complaints about motors that won't turn off, they conceded such a thing MIGHT be possible but is easily addressed by yanking the plug out of its socket.
I feel not-so-good about that.
On the whole, I'm satisfied with the troller as an auxilliary. But if we went to Catalina Island again, I might borrow a 3hp gas motor. Or not. We added oarlocks to the coamings; they work well in concert with the motor.