Scott, based on what your plans for the boat are, and having 21 years experience with a 1542 jon boat, I would say that the 30# will work fine for you. Having said that, the best advice I could give you is LET YOUR WALLET be the deciding factor.
Other than that, reading the following, and see if you might find it helpful in making your decision;
We all know an Electric Trolling motor is rated in pounds of Thrust. I have a feeling that for most of us, that really doesn't tell us anything, except maybe that a motor rated at 30# thrust isn't as powerful as one rated at 55# thrust. Right?
Static thrust only has meaning if you are pulling against an immovable object. It is like the drawbar pull of a tractor- - In low gear you have a lot of pull, but no speed. The typical trolling motor is very limited in power so a large propeller with low pitch is used so that a heavy boat can be moved, but only low speeds can be achieved.
The only true measurement of the power of a motor is the horsepower it produces. The easiest way to comapre motors is to compare the electrical power in watts that each uses. So how do we convert Thrust to Horsepower?
Multiply the battery voltage by the amp draw at full speed to get the watts of the motor you are using. Allowing for the efficiency of about 80% for the electric motors on trolling motors, you can figure on about 940 watts per horsepower. A 12 volt trolling motor that draws 35 amps uses 420 watts of power and will develop about 0.45 horsepower. The maximum current figures that trolling motor manufacturers publish are for static thrust conditions and are less when the boat is moving. A true comparison would require measuring the amp draw with an ammeter while in operation.
Now let's see if we can choose a boat that we can power by Electric Trolling motors and estimate its performance.
Choosing a boat is a personal process that involves a number of different, and sometimes opposing, factors. We all have different ideas and preferences, but we need to understand that any choice is of necessity a compromise between function, performance, comfort, appearance and cost. This article deals with the issue of performance and is aimed particularly toward fishermen and others who wish to purchase a boat for use with an electric motor. I do not presume to tell you which boat to purchase; I only want you to be aware of what is involved so that you may make an informed choice.
The speed any boat will achieve is determined by a number of interrelated factors. The hull design of a boat, the weight to horsepower ratio, and the waterline length all have a bearing on the maximum speed the boat will reach.
Many boats built today are designed primarily as planing hulls and are quite efficient when they are powered by the properly matched gasoline outboard motor and are "up on plane." It may be quite a different story, however, when they are propelled by a low horsepower electric motor.
A planing hull is designed for speed and, when powered by a motor of sufficient horsepower, slides up and over the water with most of the hull out of the water, reducing drag and allowing high speeds. Weight is positioned toward the stern to allow the bow to be clear of the water.
When a planing hull is traveling at low speed, with the hull fully in the water, the width of the boat and the heavy stern produces a large frontal area pushing against the water, requiring a large volume of water to be moved out of the way for the boat to pass, and producing large waves. The deeply submerged transom also sucks water along behind it as it moves along, increasing the effective weight of the boat (the weight of the water being dragged), as well as creating more turbulence. This condition is seen when a planing hull is initially accelerated from a standing start; the stern "digs in", and a lot of power is required to get up on plane. At less than planing speeds, this hull design and weight distribution has much more drag than a displacement hull. The only electric boats that are capable of planing are very lightweight specialized racing boats that are impractical for other purposes.
The most efficient hull shape for displacement speeds is long and narrow, like that that of a canoe. This shape moves the water aside and lets it return behind the boat with the minimum of turbulence. Turbulence causes drag and this consumes power.
Many fishermen want the comfort of a wider, more stable fishing platform, rather than a narrow canoe, but want an efficient electric powered boat to fish restricted reservoirs. These fishermen should choose a boat that is relatively narrow (especially at the transom), has a flat bottom that is not deeply submerged at the transom, and has a bow that does not plow through the water at low speed. In general, a jon boat style hull with a gently upswept square bow is more efficient than a semi-vee. Weight should be distributed so that the bottom of the boat is parallel to the water surface when the boat is at rest.
The weight to horsepower ratio is the next consideration. The lighter a boat is for a given horsepower, the faster it will move. It is important to eliminate all unnecessary weight from the boat. When considering which boat to purchase, the hull weight is one of the important considerations. A boat without a lot of heavy decking is an advantage, both because it is lighter and also because it is easier to position the battery weight to achieve level flotation.
The last consideration is the waterline length of the boat. For a given weight of boat, and a given horsepower, the longer a boat is, the faster it will move. As a boat moves through the water waves are generated. The distance between the waves increases with the boat speed. As this distance increases, the stern of the boat drops into the trough between the waves so that the boat is climbing the bow wave rather than bridging across the wave train. A large amount of power is needed to increase the speed beyond this point. (This is the point that a boat must "get out of the hole" to get up on plane.) A long narrow boat has less frontal area so a smaller volume of water must be moved out of the way to allow the boat to pass. This reduces the size of the waves and wake, using less energy.
Be sure that whatever boat you choose has enough carrying capacity to accommodate the extra weight of the batteries you will be using. 12 volt deep cycle batteries weigh about 60 lbs. Remember that many boaters would like to have a boat that is larger, but very few are sorry they didn't get a smaller boat!
opcorn: :LOL2:
