Starter Motor on 8.1S refuses to spin??

Well I'm back - and so is the problem...

Here's what I've done so far,

  1. Replaced both batteries that start the Stb Engine - still have the problem (yes I did clean the cables and posts before installing)
  2. Swapped starter motors between engines, cleaned all disconnected wires before reinstalling - still have the problem with Stb engine ONLY (rules out a bad starter since I have yet to have the problem with Port engine)
  3. Removed/tested/reinstalled slave solenoid by applying power to smaller posts and checking larger two posts for continuity, seems to work just fine every time - still have the problem.
  4. Tested starter switch by removing yellow/red power wire (that powers the slave solenoid upon starting), showed full power when starter button depressed every time - still have the problem.
  5. Tested yellow/red power wire connected at the starter by disconnecting it then testing for 12vt upon depressing the starter button, works every time - still have the problem.
Things to still try - Remove all ground wires from post on the block, clean and reinstall? Swap slave solenoid with other engine?

Any suggestions??:huh:

OK, Problem seems to have been solved - Here's the update.:smt038

Swapped the slave solenoids and took all the ground wires off both blocks, cleaned them well, reinstalled. The ground wires were a bit corroded (more on the engine that never had a problem though) which seems to have been the problem.:thumbsup:

If the slave solenoid was bad, the other engine would now have the same problem - which it doesn't. (so slaves are ok)

Moral of the story?? Problems with DC electrical - check your grounds!!:grin:

Thanks everyone for your imput.
 
Dumb question? Where is the solenoid located? Mine is doing the same thing
 
You need to understand that electrical items no matter what type need a good positive AND a good negative to work
If you had the manual , you would know. Look for something like this
72400-merc.-starter-slave-solenoid.jpg
 
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I have the same problem with the starboard engine on my 320. Just put a new Mercruiser starter on it. Made no difference. After reading the above, I guess I need to check grounds.
 
Here's how these engines are typically wired -

1. Ignition switch sends power to the slave solenoid.
2. Slave solenoid sends power to the starter solenoid.
3. Solenoid pulls in on the starter and starter engages.

In both cases the solenoid is nothing more than a large relay. Provide power to the coil on the solenoid/relay, and the switch closes completing the circuit.

Don't just assume because the solenoid is clicking that it's working. The contacts internally can become corroded and they won't make sufficient contact in order to complete the circuit. On the slave you should see the larger wires. One side should have constant 12v (if not it's likely the fuse on the starter solenoid from my recollection?). On the smaller wires you should have 12v when the key is turned. Verify you have power when the key is turned. Verify that the slave engages and you have power on the other side of the 'switch' once it closes. You can also use your ohms scale on your Digital Multimeter and put your leads on either side of the large terminals. Have a helper hit the key and you should see the circuit complete/beep.

The wire that becomes energized when the key is turned subsequently sends power to the solenoid on the starter. Test there next assuming the slave tests out. You can also bypass everything and jump the large terminals on the rear of the main starter with a large screwdriver. If the starter turns, you know something is going on upstream. With that said, Mercury typically uses a 90 amp fuse mounted directly to the starter solenoid lug. Use your DMM again and set it to the ohm scale, test on the solenoid lug side and then to the small terminal side on the fuse. You won't know it's blown any other way unless you completely disassemble it.

Hope that helps.
 
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You can also bypass everything and ground the large terminal on the rear of the solenoid to the starter case with a large screwdriver.

You can't ground the large terminal to ground, you can jump across the two big one but don't jump to ground
 
I'm having the exact same issue on my 2003 360. Replaced both rocker switches and then cleaned the connections on my starter from the advice on this thread. Did you ever get it resolved?
 
You need to understand that electrical items no matter what type need a good positive AND a good negative to work
If you had the manual , you would know. Look for something like this
72400-merc.-starter-slave-solenoid.jpg
What location would you find the slave solenoid?
 

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