Running difference between the flat-bottomed and keel boats

A lot of people are interested how speedy and maneuverable different types of boats can be with motors of different power. In order to save your nerves and money before you purchase a boat think, for what purpose you need it and what you want from it.

Actually, you have only two variants of answer:

  1. I need a boat to swim on a short distance. I want a boat for fishing on a small lake, pond or river, to ride at a speed of 3-5 km/hour with a low-powered engine of 2-5 horsepower capacity. In this case a simple flatboat is a perfect choice. These boats have a small weight, they are compact, easy to transport and assemble and take up a little space in storage.
  2. I want to travel on a long distances. I would like to go fishing in open water (or in the sea!), to ride over the waves at a speed of 20 km/hour with a powerful engine of 8-15 horsepower capacity. For all this you need a large, high-speed and spacious boat rigid collapsible deck and inflatable keelson. While choosing a boat and an engine for it you have to consider the boat type and its estimated payload: number of passengers, weight of equipment, gear, fuel.


Light flat-bottomed boat with the possibility of outboard transom installation. Maximum speed is 5-10 km/hour. You cannot use a powerful engine on it.


This type of boat is perfect for small rivers without strong flows, waves and wind. With a built-in transom and the engine with up to 10 horsepower capacity the boat can accelerate up to 20 km/hour. The only drawback of such boat is that it is unstable on the waves.


The boat is large, heavier and it takes more time to assemble. But instead you will get steadiness on the water, agility, higher capacity and payload. It’s possible to put an engine with up to 10 horsepower capacity. The boat is perfect on course even at the high speed.


If you want to get the maximum speed from your boat the loading must be done correctly. Load the boat following the rule: maximum payload should be divided in two.

We carried out the following experiment.

Let’s take a motor flatboat that is 310 cm long with 43 cm tubes diameter and the maximum payload of 320 kg. Payload divided in two gives us 320/2=160 kg.

Loading the boat: the driver is sitting near the transom -93 kg, a passenger is sitting on the  prow – 65 kg. With the motor capacity of 6 horsepower the boat runs at the speed of 22 km/hour. If we add one more passenger weighing 95 kg the total weight of the boat increases up to 250 kg. Let’s try to “compensate” the overload by using the 8 horsepower engine. As a result we get the speed of 18 km/hour and the boat cannot go into the planning mode.

Let’s change a flat-bottomed boat for the keel one with the same parameters. Three people – 250 kg, one passenger is on the prow, one is near the transom and one is at the middle of the boat. We use the same engine with 8 horsepower capacity. The boat goes into the planning mode and shows the speed of 29 km/hour.


  1. Keel boat with the engine considerably exceeds the flat-bottomed boat.
  2. The boat must be loaded correctly, the cargo should be distributed evenly.
  3. If the prow section of the boat is raised at a full speed it is necessary to load it before going into the planning mode.
  4. If there is only one person in a boat sitting near the motor the luggage should be located in the prow.
  5. It is very important to align the angle of engine inclination correctly.