wikiHow to Buy and Install an Outboard Motor

Buying an outboard motor can be a large investment, and one which should last a long time. Choosing the right size and type is critical to getting the most enjoyment for your money.


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    Check the ratings and recommendations from your boat manufacturer. In the U.S.A., the Coast Guard has regulations governing the size of motor as well as the number of passengers on commercially manufactured boats. Never exceed these guidelines. If you do not have a Coast Guard specification plate on your boat, ask the dealer to advise you. Just basing the size engine on the size of boat is complicated, for example, a 12 foot (3.7 m) john boat or light aluminum boat will only carry a 15 to 25 horsepower motor, but a heavy fiberglass boat the same length might go as high as 60 horsepower or more.
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    Determine your speed requirements, and if you are towing water skiers, nets, or tubes. The smallest motor that will do the job is most economical, both in initial cost and fuel usage.
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    Look at the ratings in publications like Consumer Digest, and ask local boat owners about the various brand motors and their different features. There are a lot of brands to chose from, and knowing the availability of parts and the durability of the motors will help you chose yours.
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    Look at the different accessories you may chose. Some have hydraulic tilt, cable steering, and electric start, all of which simplify using the motor, while others have a pull rope start and a tiller handle for steering and throttle control. Because of these factors, no one piece of advice or article can cover all the possibilities. If you already have the boat, however, you need the compatible motor to your setup. In other words, if you have a steering wheel, or stick type steering system, you will want to buy a motor with a steering cable attachment, and if you have a battery and wiring to an ignition system you will want electric start. On the other hand, if you do not have these features in your boat, it is not practical to buy a motor that uses them.
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    Look at the different type of motors. Most outboards have two cycle water cooled power-heads, or engines. This means mixing oil either in the fuel tank, or adding it to a reservoir for an oil injection system. There are air cooled 4 cycle motors on the market, in smaller sizes, and these are usually less expensive than the two cycle counterparts.
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    Measure your transom height, so that the power-shaft, or the distance from the power head to the motor foot, where the propeller is, is the correct length. When the motor is attached to the transom, the propeller must be below the bottom of the boat to draw water and operate correctly. Too long of a shaft will drag on the bottom in shallow water, limiting the locations it can be used and eventually ruining your prop, motor foot, and even your motor. The top of the propeller blade should be slightly lower than the keel of the boat when it is in the vertical position.
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    Follow the manufacturer's instruction when you install your motor. Normally, the motor has two clamp bolts that fit over the top of the transom and tighten against it like a "C" clamp. These usually have short pivoting handles to turn the bolts, so that they can be tightened by hand, without over tightening them. They may also have holes in the so a lock can be place through each one, and secured to prevent someone from stealing your motor.
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    Use a safety cable in case the motor hits a submerged object and is knocked from the transom. This has happened many times, and the cable will keep the motor from sinking in this unfortunate event.


  • Be sure to read and understand the owner's manual, and follow their instructions carefully to enjoy your new motor for a long time.
  • Look for a package deal on the accessories for your motor. You will also need a fuel tank, fuel lines, a flushing attachment for cleaning the engine, and possibly a support bracket if you are towing the boat on a trailer. Often you will save money buying these items packaged with the new motor.
  • Read a few outdoor or boating magazines so you can be familiar with problems manufacturers may be having with their product, as well as becoming literate about features, specifications, and performance data.
  • Talk to local fishermen or other boaters about the size they recommend for your boat. Salesmen may suggest the largest size the boat will handle, when a smaller unit is more practical.
  • Look in the want ads when you have selected a size and type of motor. Many "fair weather" boaters will replace their motors every few years, and these may offer you an alternative to the high cost of a new unit.


  • Do not overpower your boat! Putting a motor which is too large for your boat is extremely dangerous!
  • Be careful with the fuel both in transporting it and in using it. Fuel leaks are not common on outboard motors, but when they occur, often they have deadly results.
  • Have on board, and use all the required safety devices required by law, such as flotation devices, a signalling device, a fire extinguisher, and running lights for nighttime use.

Things You'll Need

  • Depending on the size of your motor, you may need a strong helper, or even a lift or hoist to install it.

Article Info

Categories: Boat Motors and Marine Engines