Starter or Solenoid?

[jim_s]

The reliable old Mercury 90hp 3cyl 2-stroke has had trouble starting the past few outings. Trouble as in, turn the key, and sometimes (increasing frequency of sometimes...) nothing happens - no action, no noise, no smoke, no go. I thought it was the ignition switch, as wiggling the key seemed to help, but it seems that was really just a matter of trying multiple times until things started happening.

I've got 12v to the solenoid from the battery. When the key is turned, the solenoid clicks, even when the starter doesn't raise the gear or spin. With the big wire from the solenoid to the starter attached to the starter, I get no voltage out of the solenoid when the key is turned and the solenoid clicks. (So I'm thinking, "AHA! It's the solenoid!") BUT, with the big wire between the solenoid and starter disconnected, I get 12v out of the solenoid when the key is turned and it clicks.

So, I'm thinking at this point that the problem must be the starter, itself.

Anyone with more smarts than I have on this stuff, happen to have any helpful diagnosis or further diagnostics to try to figure out what part I need to order?

Thanks!

 

[jim_s]

Further diagnosis - shorting the large red wire coming into the solenoid, directly to the positive terminal on the starter motor, results in the starter spinning and the starter gear engaging, while turning the key won't do so. So, I guess I'm back to it being the solenoid...?

 

[Texasmark]

The solenoid high current contacts are pitted from age. Pitted contacts can carry ohm meter current but not 150 or so amperes necessary to spin your starter. Yepper solenoid renewal time.

 

[jim_s]

Ding! Ding!! Ding!!! Solenoid it is! Swapped it out with a new one, and all is now good!

 

[jim_s]

To bring home Texasmark's point - this was the inside of the old solenoid. Surprised it went for as long as it did!