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How to troubleshoot outboard motors

Yep, we’ve all been there. Hunched over the back off the boat yanking the pull-cord with increasing desperation! Guest poster, Mindi Braswell, from Aboard Marguerite shares how to quickly diagnose and troubleshoot outboard motors. Plus, we’ve a included a bonus “$#!T my engine won’t start” checklist at the bottom of the post.

I’m not a professional marine mechanic, but I’ve definitely learned a thing or two working with the little Yamaha 6.6 outboard on our Seafarer 26, Marguerite.  While each outboard make and model functions a bit differently, there are few things that are universal to all outboard motors. When our engine won’t start, this is how we tackle it.

1. Is everything properly attached and in the right place?

If you’re having trouble getting your outboard to run, it may be something simple. Check that hoses are properly attached, that there are no issues with dry-rot, and that there’s no place where air might be getting in the fuel line.  Also check hoses to make sure that fittings are functioning properly (there’s a reason they sell the little fittings that attach to the fuel tank and engine as independent parts).  It may also be that fittings or clamps need to be adjusted (such as the tiny clamps that attach the small fuel filter to the fuels lines). Be sure that you know and understand how to work your motor’s choke (whether you need it in the in or out position and when it’s best to switch from one to the other).  Also be sure that the safety fitting (that’s designed to be pulled off should you fall overboard) is in place. Again, these frequently dry rot and break, and your engine may be designed to not start without it.

outboard motors

2. Is fuel running properly?

Check spark plugs (they shouldn’t be bone dry and they also shouldn’t be drenched).  Be sure that they’re not covered in carbon, and sometimes it helps to check the gap (they make a gauge for this specific purpose).  Spark plugs should be tightened into place (it can be REALLY problematic if they aren’t fully screwed in). If it’s not a spark plug issue, check other simple solutions.  

Is the engine getting fuel? If it’s an electric start, do you have enough battery power? Also be sure to check the fuel filter, particularly if the engine has set for a period of time.  You may not necessarily need to replace the fuel filter, but you should be able to blow through it easily. Even the tiniest of sediment can create a problem with the flow, so be sure to check for that

3. Is water flowing?

If your outboard motor isn’t “peeing” (that’s what my 2-year old calls it), you may have a problem with the impeller. The impeller is designed to run water through your motor keeping it cooled. The motor should shoot out a small, steady stream, typically to the starboard side of the boat. If that isn’t happening, you will burn up the engine, (which is NO BUENO). If part of the impeller has broken off, you risk that piece getting stuck elsewhere in the engine which can create issues down the line.The moment you notice that stream isn’t happening, definitely STOP the engine and regroup. And for what it’s worth, changing the impeller isn’t a horribly scary thing. For our outboard motor, it did require removing the foot and the entire bottom assembly. While this sounds a bit unnerving, it simply means that you have to be careful to align things properly once you’re ready to reassemble the engine. For tools you’ll need a hose and something called flush muffs, which literally look like earmuffs for your outboard motor and allow the water to flow through when you have the motor pulled to work on it. Also, be sure to check that the water intake isn’t blocked.

4. If it isn’t any of the above….

It could be any number of other things, but it’s usually something simple OR just a simple quirk related to your specific engine.  Our outboard motor, for example, runs really well once she’s warmed up, but has a tendency to flood or foul out plugs early in the process.  I’ve learned to just unhook the fuel line, continue to crank and let it run out the unnecessary fuel, and when it starts, run it for a few seconds before reconnecting my fuel line.  

A lot of what happens with your engine will likely be figured out through trial and error. If it just isn’t that simple to figure out, I would definitely recommend using Google, YouTube, or phone a friend before consulting a small engine or outboard motors repair shop. We’ve replaced our impeller, fuel filter, and spark plugs and did so relatively easily with absolutely NO PRIOR EXPERIENCE.  (And by no prior experience, I mean that the closest I have ever come to working on any type of engine is taking my car to have an oil change done.)

Take your time, have some confidence, read a little, and develop your skills. It’s well worth your time and energy to do so. Me? I’m glad I took the time to get to know our outboard motor, the  couple of scratches on my knuckles has saved me cash for more boat drinks. 😊


Waterborne’s “$#!T my engine won’t start” checklist

  1. Check choke and adjust
  2. Check priming bulb and prime
  3. Check fuel connection
  4. Check for vacuum from the fuel tank (crack lid or fill port to equalize pressure)
  5. Check spark plug for fouling
  6. Check for spark by touching the threads of the spark plug to the engine block and turning over the engine
  7. Check fuel filter
  8. Check for fuel or oil leaks in the engine

You can follow Mindi Braswell’s adventures at: mindi.aboardmarguerite on Instagram, marguerite0716 on TwitterAboard Marguerite on Facebook, and Aboard Marguerite YouTube channel.

Timothy Duncan

Thursday 16th of August 2018

It's funny how your kid describes the water coming out the side of the outboard motor. Kidding aside, it is indicative of a serious engine burnout if the water does not cool the engine. I am planning on going fishing near the swamp in 2 weeks, making sure the water intake lines are not impeded would be a cool place to check to prevent getting stranded.

steve thompson

Sunday 24th of June 2018

Typically two stroke motors suffer from gumming up of the carby. This is where fuel deposits restrict the main jet (fuel flow to the engine) and when this happens the motor will either not start or only run with the choke on and not rev. Proper solution is to strip the carby and clean with carby cleaner. Quick and dirty is to squirt carby cleaner into the carby and hope it soaks into the main jet and dissolves the gum. Cheers Steve

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