TROLLING MOTORS - CHOOSE YOUR THRUST WISELY
One of the first considerations in purchasing a trolling motor is how much thrust you will require. Now, this can be a very tricky question because of all the variables you are required to consider. There are several guidelines to assist you in this decision and then the rest is up to your personal taste or style of fishing.
First off, although it is frequently quoted, trolling motor thrust cannot be correlated to Horsepower. They are two entirely distinct calculations. The exact definition of one horsepower is 33,000 lb.ft./minute. Put another way, if you were to lift 33,000 pounds one foot over a period of one minute, you would have been working at the rate of one horsepower. Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a proportional but opposite force on that system. Simply put, trolling motor thrust is a generated force, equal to the amount of net force required to accelerate a mass of one kilogram at a rate of one meter per second per second. See the difference? Clear as mud, right?
All the engineering confusion aside, let’s take a look at some different factors. If you ask Minn Kota or Motorguide customer service, the most popular trolling motor manufacturers, what they recommend you will get the same answer. Their answer is based on boat weight; two pounds of thrust per 100 pounds of a boat loaded to capacity as a minimum requirement. Loaded to capacity means the weight of the boat plus the advertised maximum capacity for persons aboard the vessel. If you have a 1500 pound boat with the maximum capacity of four people at 650 pounds; your minimum thrust requirement would be 1500+650/100 x 2= 73 lbs of thrust.
The other table most frequently found is based on boat length. This table is not as simply calculated and I have no idea where the figures come from, but both tables are below for your consideration.
Boat Length(ft) Minimum Thrust (lbs) Maximum Weight (lbs) Minimum Thrust(lbs)
12’-14 35 1500 30
15’-16' 40 2000 40
17’ 50 2500 50
18’ 55 3000 60
19' 65 3500 70
20' 75 4000 80
21' 80 4500 90
22+ 80-101 5000 100
If your boat happens to fall into two different thrust categories based on these charts, we'd suggest using the minimum thrust figure recommended via the weight method, since it is the number one consideration and the most consistent calculation.
Thirdly, you want to consider your type of fishing. If you mainly fish brush piles and drop offs in the lake you can take the next category up from you calculated minimum trolling motor thrust and be in relatively good shape. However, if you fish a lot of rivers and bodies of water that have noticeable currents, or you prefer trolling down the banks using a crank bait all day, you may want to consider moving up a couple classes from your calculated minimum trolling motor thrust.
There are several more factors to consider such as budget, required voltage, shaft length and what bells and whistles are worth your hard earned money. I will not try to address all these in one posting. Just remember, more power is usually considered a good thing; but an overpowering trolling motor has its’ faults as well as an underpowered trolling motor. Do your homework before you buy! Then come see us at DJ's Marine Electronics to save a few bucks!
One of the first considerations in purchasing a trolling motor is how much thrust you will require. Now, this can be a very tricky question because of all the variables you are required to consider. There are several guidelines to assist you in this decision and then the rest is up to your personal taste or style of fishing.
First off, although it is frequently quoted, trolling motor thrust cannot be correlated to Horsepower. They are two entirely distinct calculations. The exact definition of one horsepower is 33,000 lb.ft./minute. Put another way, if you were to lift 33,000 pounds one foot over a period of one minute, you would have been working at the rate of one horsepower. Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a proportional but opposite force on that system. Simply put, trolling motor thrust is a generated force, equal to the amount of net force required to accelerate a mass of one kilogram at a rate of one meter per second per second. See the difference? Clear as mud, right?
All the engineering confusion aside, let’s take a look at some different factors. If you ask Minn Kota or Motorguide customer service, the most popular trolling motor manufacturers, what they recommend you will get the same answer. Their answer is based on boat weight; two pounds of thrust per 100 pounds of a boat loaded to capacity as a minimum requirement. Loaded to capacity means the weight of the boat plus the advertised maximum capacity for persons aboard the vessel. If you have a 1500 pound boat with the maximum capacity of four people at 650 pounds; your minimum thrust requirement would be 1500+650/100 x 2= 73 lbs of thrust.
The other table most frequently found is based on boat length. This table is not as simply calculated and I have no idea where the figures come from, but both tables are below for your consideration.
Boat Length(ft) Minimum Thrust (lbs) Maximum Weight (lbs) Minimum Thrust(lbs)
12’-14 35 1500 30
15’-16' 40 2000 40
17’ 50 2500 50
18’ 55 3000 60
19' 65 3500 70
20' 75 4000 80
21' 80 4500 90
22+ 80-101 5000 100
If your boat happens to fall into two different thrust categories based on these charts, we'd suggest using the minimum thrust figure recommended via the weight method, since it is the number one consideration and the most consistent calculation.
Thirdly, you want to consider your type of fishing. If you mainly fish brush piles and drop offs in the lake you can take the next category up from you calculated minimum trolling motor thrust and be in relatively good shape. However, if you fish a lot of rivers and bodies of water that have noticeable currents, or you prefer trolling down the banks using a crank bait all day, you may want to consider moving up a couple classes from your calculated minimum trolling motor thrust.
There are several more factors to consider such as budget, required voltage, shaft length and what bells and whistles are worth your hard earned money. I will not try to address all these in one posting. Just remember, more power is usually considered a good thing; but an overpowering trolling motor has its’ faults as well as an underpowered trolling motor. Do your homework before you buy! Then come see us at DJ's Marine Electronics to save a few bucks!
