When trying to start my Yamaha Waverunner, it makes a loud humming sound, but will not attempt to turn over.?

Question

It is a loud buzzing sound when I push the start button. With the key in alone, all of the lights come on, so I don't think it is the battery? It buzzes when I push start, but the engine doesn't even try to crank.

Answer 1

Sounds like the engine is siezed and the starter is not able to turn the engine.  The hum would be the stalled starter.  Might have water in the cylinder(s).  Pull the spark plug and try to turn the engine with the starter.  If it now turns and spews water from the plug opening, you will need to take it to a mechanic for service.

Answer 2

sounds like the starter is not engaging.

Answer 3

Even though the lights come on, that doesn't mean that your battry is charged.  We run Yamahas in our harbor, and I can tell you from experience that if the battery is not at least 12.1 volts, the lights and display will come on but the engine will not turn over.  Your local parts store should be able to test your battery for you, if you do not have a volt meter at home.  If the battery needs to be charged, do not attempt to charge the battery unless it is completely disconnected from the waverunner, because you can end up shorting out the electrical system.  If the battery has plenty of voltage, then the next thing to do is pull the spark plugs and try to turn the engine over to see if you have water in the cylinders.  This really only happens if the waverunner has been upside down and was not turned right side up correctly.  If you find water in the cylinders, then check the oil to see if there is any water present in the crankcase(4-stroke models only).   If you do not see any signs of water, such as milky brown oil or small droplest on the dipstick, then you can probably get away with putting fresh spark plugs in and running it.  If there is water in the crankcase, then you need to do an oil change(if the oil is extremely milky you may need to change it multiple times to get all the water out), run it for a short time, and inspect the oil again.  Run it for about five to ten minutes then check the oil again to see if there are signs of water in the oil, as this can be a sign of internal problems, i.e., broken head gasket, cracked head, or a cracked block.  If the oil is mostly clear, then it may just be residual water from the oil change and you'll need to check it the next couple times you run it to make sure it doesn't get worse.  And only run the waverunner with a source of water, or you could damage the engine. If you pull the spark plugs and it still won't turn over, then the next place to look os the starting system itself.  Locate the starter.  Take a small hammer or other hard tool and try tapping the starterwhile pushing the start button.  Because they are constantly exposed to moisture, marine starters have a tendency to stick if they sit for any length of time.  If the starter still does not turn the engine, then you need to remove the starter and have it tested.  If it tests good, then you may have an internal engine problem.  Sometimes, though, pulling a starter and the trip to the parts store to test it can shake things loose in it, so put the starter back on and try to start it.  If you still get nothing, then there is a good chance that there is a serious problem with the engine and you will either have to tear it down yourself, or send it to a shop.