Mercury 15HP 2 Stroke - Electric Start Not Working

Make sure the starter bolts attaching it to the block are tight.
If loose the starter may not be fully grounded and blocking full current flow.
Enough ground for the solenoid, but not for the amperage needed for the starter.
And starters do short out, especially in the marine environment.

This link is meant for automotive use, but the process is the same.

http://www.misterfixit.com/starttst.htm

 

Do NOT tap the starter with a hammer!!!!!!!!!!!!!, if you do, chances are your going to need a new one for sure

 

Make sure you battery has enough juice, my Merc 25 had the same symptoms after I nearly toasted the battery... The starter was fine, just was not receiving enough power to spin up.

 

If you heard the solenoid click check the battery, then check the solenoid, then the starter. If is was kill switch you should not hear anything.

Battery should be up around 12.8 volts, if it is down to near 12 volts or less it needs to be charged or replaced. Try charging first. Assuming all is well.

Solenoid is nothing more than a electromagnetic switch, when current is applied one side is magnetized and "lifts" an internal contact across the battery in and battery out poles completing the positive wire to the starter.

Take the negative lead from a multi meter and ground it on the motor, take the positive lead and hold it to the energizer wire (small wire that goes to solenoid from starter switch) hit start switch you should read battery voltage.
Assuming all is well.

Take a jumper cable (only use the red side) hook to positive side of battery and the hook to battery+ out pole of solenoid. If starter works then bad solenoid. You MUST NOT touch motor or any metal parts. Once on the water I cut a square out of the top of a plano box to use as a shield to do this to combat a failed solenoid.

If the above did not work then most likely starter is bad.It is really best to remove starter to test.

 

Oooops.... :-[ been there done that when all else failed 18 miles offshore.
It was enough to change the position of something in the starter so it would and we got home.
A little r-n-r (remove and replace) took place before the next trip out.

I was raised in the school of "if at first you don't succeed, get a bigger hammer!."

 

Like every one else has said, check your battery is fully charged,

Make sure all connections are tight,

Next jump the starter if it works then replace the solenoid

Do this by taking a small peice of 4-6 gausge wire and  touch it from the battery hot side on the solenoid to the hot post directly on the starter.

Also if your kill switch was bad it would turn over all day long it just wouldn't fire off, as the kill switch interupts the fire of the enige by shorting out to ground before the coils. (so the starter would work just fine) Now if it were the saftey netural switch you wouldn't hear anything.

 

Yes, I'd replace it.
Resistance can be checked for using a volt/ohm meter.

 

As Brett said replace any wires that are corroded .

Did you take a jumper wire from the hot side of the solenoid (this will be the + wire coming from the battery attaching to the solenoid) to the Starter directly? There is a stud that sticks out of the starter motor that has a wire going from it to the solenoid.

Use a heavy gauge wire 4-6 about a 12" long and jump from the solenoid to the starter, it will arc and throw a spark a little, but the starter should engage. If it doesn't you have a bad starter. Make sure when you do this your kill lanyard is in the off position so the motor doesn't start.

 

Disconnect the cables from the boat battery.
Grab a set of automotive jumper cables.
Ground the starter to the negative terminal of the battery
connect the red side of the jumper to the positive terminal of the battery
and touch the red jumper to the positive stud to see if it spins.

 

Which is why when testing, the starter is removed from the engine
and worked on at the bench...

 

Dead starter. :'(

 

I''ve attempted it, killed a weekend. 

Much easier to take it to a rebuild shop and swap the old one for a rebuilt one.