1996 Mercury Force 120XR SportJet - Won't Start

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dcaplan

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Jun 19, 2017
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Hello,

I put the boat in the water for the first time this year and it wont start. The started engages for a few seconds and than quickly disengages but continues to spin but not in the flywheel. After a few attempts it will engage in the flywheel but not move it (although you can tell it is attempting to). I pulled the battery and had it tested and the results came back that it is still in great condition. I tried a second battery with exactly the same results. Since it does not seem to be the battery I am thinking it is either the started or the solenoid. I did notice the starter very hot to the touch and a little smoke from it. I tried moving the flywheel by hand via a socked on the top and it is not locked up and had compression. In the past I have noticed the boat very hard to start the first of the year but this is the first time it has done this. Any thoughts?
 

jerryjerry05

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Remove the plugs and try turning it over.
Then do a compression test.
Post the results.
​The slow turn could be bad connections,bad starter, bad power cable.
Welcome.
 

dcaplan

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Hello, ran a compression test, 3 at 110 and 1 at 105.

I tried with a borrowed battery, same issue. I ran directly to the starter with jumper cables, same issue. Here is a video of the issue:

https://www.youtube.com/watch?v=Ca6v_Zgkh5w

I did try with a new starter I ordered from ebay but it was the same results but I am not thinking too much about that because when it arrived it was clearly cheap overseas junk.

I can literally turn the motor with a socket by hand so the starter should be able to turn this correct?
 
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Rhys62

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Sep 14, 2014
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Sorry I'm late did you fix it? I had similar issues with my sportjet 90 the fix was tear the starter down clean it up reassemble and used a white lithium grease on the traveling gears slide instead of the heavy grease the previous owner had used. I cleaned the parts with carb cleaner and LET THEM DRY OVERNIGHT. carb cleaner is very flammable so let them dry overnight or you'll have a boat fire.
you can also put a volt meter across the solenoid contacts (the big ones from the battery and to the starter) you will read 12 volts when the starter is not being powered and 0 when it is it, if it isn't 0 volts when the key is clicked on and the starter is trying to run your solenoid is bad.

​I noticed in the video at the end your starter gear didn't disengage from the flywheel might check alignment of the shaft.
 
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dcaplan

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No the problem still persist!

​I noticed in the video at the end your starter gear didn't disengage from the flywheel might check alignment of the shaft.

Thank you very much for the advice, I will try this tomorrow. Also, when you say check the alignment of the shaft, do you mean the alignment of the starter motor? How do you adjust the alignment? I tried playing with the two top bolts to adjust the alignment but I couldn't seem to get it to move much.

Thank you very much!
 

Rhys62

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Sep 14, 2014
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while you have it off hold it to the ground and power it see if the shaft is bent or something. if seated correctly into the mount it shouldn't move so the alignment should be correct the sticking could just be old grease and grime that the clean up will resolve. other things to look for is while cranking (use short cranking times and let it cool between. check the voltage at the battery then each side of the solenoid and finally at the starter. there should only be a VERY small difference in voltages. if you find a 1 or 2 volt or more drop whatever is to the battery side is your issue. if you get all the way to the starter and you have only a small change, brushes in the starter possibly or bad windings. Does she spin well with the plugs out?

​Oh and jumper cables you used where they bigger wire than the wiring on the starter? if not you may not have a good test since the clips may not give as good a connection as the normal wires.

​Keep in mind a voltage drop across a piece of wire or solenoid means something isn't right between that point and the battery (corrosion bad wire, bad connection, bad crimp in a cable or bad contacts in the solenoid.) electricity is very predictable it will flow until it is slowed down or stopped.
 
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pnwboat

Rear Admiral
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Oct 8, 2007
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The starter gear will not disengage from the flywheel until the motor starts. The starter gear staying engaged is normal if the motor doesn't start. There's enough pressure or friction to hold the starter gear against the flywheel. Once you resolve the problem, and the motor starts, the gear will automatically disengage from the flywheel.
 

jerryjerry05

Supreme Mariner
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May 7, 2008
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Clean rebuild the starter.
Use oil or a thin grease(white lithium spray).
​Check the battery cables. Any soft or swollen spots?
The cable connections: ground on the block?
 

blackd

Petty Officer 2nd Class
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Sep 27, 2013
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152
Just fixed the same issue with my 97 120HP. It was the starter relay/solenoid. Motor now has new starter and relay/solenoid. Now to run it on muffs to see if the carbs are OK. This is the first time the motor has been run since last Fall.
 

dcaplan

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Jun 19, 2017
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Just fixed the same issue with my 97 120HP. It was the starter relay/solenoid. Motor now has new starter and relay/solenoid. Now to run it on muffs to see if the carbs are OK. This is the first time the motor has been run since last Fall.


Thank you for your input as well, thank you everyone! I am going to rebuild the starter and replace the wires this week. I figure since the boat is 21 years old I will simply replace the battery wires as a basic maintenance anyways. I will report back!
 
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