Just starting a pocket crusier and would like some input on this idea? i would like to keep the depth of the keel on the back and mount the trolling motor head in a cut out area back there(like a regular sailboat). It would be fixed with a guard below. I dont mind losing the beaching ability and i'm curious about how much speed i would lose ( don't mind if I lose some). I'll be doing mostly slow crusing on a well protected lake. Any thoughts, thanks
Much depends on the size of the motor and the prop used. You will not lose much speed except under sail (maybe a half a knot, probably more), but you will lose a valuable aspect of a trolling motor, which is it's steering ability. Yes, you can use the rudder, but steering response from a tolling motor is way far superior to a rudder and also work instantly, while a rudder only works if the boat is moving.
If you make a fixed motor, you will have potential for a leak too. Considering the sailing speed is less then 5 knots for a PC, kissing off any speed is a substantial lose. This coupled with the fact that standard trolling motor props are geared to push you to about 3 knots, using a trolling motor for more then occasional motoring isn't as wise a choice as seems at first blush.
On the other hand, if you use a big trolling motor and re-prop it, you could get to hull speed and more, though at the cost of amp hours you have aboard.
Bottom line is cruising speed and range with the battery capacity selected. Using a 55 pounds of thrust motor (about as big a 12VDC as you can get) a single 100 amp hour deep cycle battery will offer you about two hours of cruising time at 3 knots on a PC, maybe double this at 2 knots. If you have only short distances to travel or only need to motor along occasionally, a trolling motor is an easy way to go. If you want to motor a lot, then doing 2 to 3 knots will seem like you've brought your evil mother in-law along for the ride.
Thanks Paul I knew you would be the one to respond. I just hate having the the thing sticking out the back. I love the real catboat look and it just doesn't look good. The lake i'm on is also dead quiet even in the middle of summer ( dont people go to Maine anymore, the last week up we saw one motorized guide boat the whole time and its a really large lake. Hey better for me I guess!). Always read your posts Paul Thanks.
I would also advise against mounting a trolling motor in the keel. Aside from Paul's comments, with which I agree, there's also the problem of the permanence of mounting a trolling motor in the keel. While I love electric motors, I haven't found them to me entirely trouble-free, multi-year motors, from any manufacturer. A few years, perhaps. Transom mounting will be much easier, less drag, and allow for easier maintenance.
On another note, how cool that a nice area like yours is less crowded!
Mike
Don't get me wrong, I use a trolling motor to get me out on my local puddles. It's just that I only need it occasionally and never more then a mile or two. Most folks can live with puttering along at God awfully slow speeds for a half hour or so.
I've also designed electric systems that really do much better then typical trolling motors can. These systems rely on "capacity" which in most cases is how much weight in batteries the hull can tolerate. The last system I did was a 36 volt, butt kicker and each battery was 160 pounds! It was much more costly then any outboard, rivaled a diesel inboard setup in weight and cost, but it didn't need fuel, didn't smell and made no noise, plus was the only "powerboat" able to work it's particular waterway at speed, while everyone else puttered along with a trolling motor, sails or hand power.