I'm new to boating. I recently purchased a used boat that has a 9.9 Yamaha 4-stroke outboard motor.

The previous owner showed me that the motor works, by running it for a second while the boat was on the trailer.

He gave me a few tips about how to operate the motor and said I shouldn't run it while it's not in the water -- since it's water-cooled and would overheat. I've never operated a motor boat, so I'd like to try to start up the motor at home a few times before using the boat in the water. (I'd like to get the hang of it first since it seems like starting an outboard can be a bit fiddly.)

Is there a way that I can start the motor a few times when it's not in water -- without risking damage? For example:

A. Start it for a second. Let a cool for a few minutes before starting again.
B. Or, when testing, would it help to place the bottom part of the motor in a large container of water to cool it? Or is that unnecessary?

  • Starting it up for a couple seconds and then letting it cool completely should be fine, provided you don't make a hobby of it. Trying to submerge the entire bottom of the motor will likely require a very large container (55gal drum?). If you insist on running it longer or repeatedly, I would locate where the water inlet is and connect a hose to this port.
    – erfink
    Jun 2, 2023 at 8:11
  • Aside: don't even attempt to start the motor unless it is properly mounted. Jun 2, 2023 at 15:33
  • I'm new to boating and I've never operated a motor boat. That's why you should not try to start it at home. Do exactly as you've been advised until you have enough experience to make informed decisions. Placing the bottom part in a tub sounds even worse, when you haven't the remotest idea what's going to happen. Will the screw turn? Will it shred the bucket and propel shards of plastic at you? He said I shouldn't run it while it's not in the water so don't. Jun 2, 2023 at 16:01
  • Lastly, you know the motor starts. It would be better to take the boat to a place where there are others boaters. Then you can get help and advice if you can't start it. Jun 2, 2023 at 16:14
  • in most places I know, you now need a license to operate a 9.9hp (in some places it used to be required for 10hp and more - hence the 9.9 - but that value was lowered)
    – njzk2
    Jun 30, 2023 at 20:40

3 Answers 3


A Flush Muff is an inexpensive and essential piece of gear for your outboard. It looks a bit like a set of ear muffs. It is two rubber cups with a steel arm connecting them. One cup has a hose attachment. You slide the rubber cuffs over the water intake on the lower part of the engine. You turn on the hose and water will squirt out the sides. You start the engine and water should squirt from the "tell" at the back of the engine. By the way, this is the point of the tell, to let you know water is circulating properly. You can run your motor as much as you need this way. You should flush your motor every time you finish using it, if you want to make it last as long as possible. I definitely flush mine every time it is in salt water, or I go somewhere sandy.

There are two things you are protecting with the water -

  1. overheating, as you already said. Obvious how that works.
  2. the rubber fins on your impeller. The water lubricates the rubber fins as they spin in the bottom part of your motor to pump water up and through the engine casing. You can damage the rubber fins or make them wear sooner by running the engine at all without the water lubricating the rubber. Its not the worst thing to run it for a second if you have to, but it may not be nice to your impeller.

If you want to do a relatively simple DIY task, replacing the impeller is not usually a hard job and is a normal piece to wear out. I would probably replace it on a motor I don't know the maintenance history of.

This video shows you how (from BoatUS.com, a great resource) https://www.youtube.com/watch?v=e9fZ5ykTne4

TLDR: Get a flush muff ($10) and use it.


I'm new to boating and I've never operated a motor boat. That's the first thing you need to care about. Boating is fun and generally a very safe recreation activity, but only if you know the rules and your limits.

  • First, you need to know the local regulations of the lake/river you are intending to use your boat on. Depending on where you are, running a 10 hp engine might require a boating certificate. Not having one is then obviously an offense.
  • Same might apply for the boat as well. It might need registration and possibly there are taxes to be paid.
  • Then you need to make sure you carry the mandatory safety equipment (if there exist any such requirement). This might include first aid kits, tools, roars (in case the engine fails) and certainly life jackets. Even if the local legislation does not require you to carry those items, it is in your own interest to keep a minimum set of safety equipment, which most certainly should include a life jacket. Buy a self-inflating one that can (and shall!) be worn at all times.
  • And then, even if there are no regulations requiring a boating license or a registration or anything, you still need to know the rules of water traffic, called International Regulations for Preventing Collisions at Sea (COLREGS) or the corresponding local amendments to those. These for instance say that you must give way to sailboats when using an engine. And that on the water there's always right-lane-traffic (oversimplified!).
  • Oh, and of course boating needs practice, too. It's a bit like learning to drive, but with a few extra quirks, the main one being that there are no brakes on a boat that let you just stop when you don't know how to continue. And that you are significantly affected by weather.


So, please, before you even attempt to start the engine, make yourself familiar with the required regulations and the handling of your boat. You don't want to crash or sink it on your first trip out, anyway. Consider taking boating lessons. It's for your own safety.

And finally about the engine

The best way to test an outboard engine is in a large barrel (like in the left picture here). You need safely attach a holding plate to the barrel, so you can mount the outboard to it or have some other method to keep it safely in place. Make sure that you don't drop the whole engine in the water, that could damage it. Be very careful if you shift into gear, as this might create a push strong enough to tip everything over.

  • 4
    While this us good advice for a boating newbie, it doesn't really answer the question at all.
    – bob1
    Jun 2, 2023 at 22:50
  • @bob1 True. Due to all the other concerns in the question, I had forgotten about the actual issue. Now updated.
    – PMF
    Jun 3, 2023 at 4:59
  • 2
    For someone who is completely unfamilar with boats and their engines, I would say jerry-rigging it to a plastic barrel is a disaster waiting to happen. A translation of the website reveals that this is to decalcify the internal water channels with a solution of citric acid in the barrel: it says nothing about a beginner experimenting with something they know nothing about. IMO only a skilled user or mechanic should set up this rig. Jun 3, 2023 at 19:20
  • @WeatherVane Possibly, therefore my emphasis on caution and my lengthy introduction. I do fear the OP is taking things a bit to simplistic. Googling does find quite a few pages showing this setup.
    – PMF
    Jun 3, 2023 at 19:33
  • Perhaps they do: appropriate for expert users. I think the emphasis should be not to attempt anything that a beginner could get wrong. Heck, they don't even know the throttle reponse, or how to mount it securely... to somewhere it is not designed to be fitted. The guy selling it demonstrated that it does run, but that doesn't mean a beginner can safely try it. Jun 3, 2023 at 19:40

Putting the motor in a bucket of water worked fine since it's such a short motor. I can tell the motor is sucking up water for cooling because it's spitting water out of the drain hole.

Nice and simple.

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