Is this correct? Positive goes to the top, negative to the bottom? I'm thinking I did this wrong and that it is negative at the top and positive at the bottom... I'll go double-check on my 300SD. In any case, how would I use this to jump an engine out of the car? + to +, - to -, obviously, but what should I do for a ground? Can I go battery + to starter +, battery - to starter -, starter - to the engine?

I'm trying to jump my spare engine.

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1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

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Catch it coming out of a bar late at night, sneak up behind...oh - not that kind of jump

Ground strap from your battery to the engine block. Power to the red X on the silenoid in your picture. Use a jumper from the red X to engage the silenoid.

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You can't always get what you want, but if you try sometime you just might find you get what you need.

Doesn't look right to me, but I don't have a starter in front of me. The big stud you show as "+" should go to BATT+. BATT- should be thru the frame of the starter, so clip a jumper to a mounting ear. That alone will not actuate your starter, it is how it is wired in the car. There should be a smaller "start" connection which actuates the the solenoid (big clunk sound), which should apply +12 V to the solenoid output that you label "-", which goes to the motor. You don't normally hook anything there, though you could bypass the solenoid by applying +12 V there to check the motor alone. BTW, I have actuated M-B starters like this outside the vehicle, I just don't recall where the "start" terminal is.

That negative terminal in your photo will become positive as soon as you activate the solenoid, giving you a dead short. It's simply the solenoid output to the starter. As others have pointed out, the case is the negative part of the system. Make sure the starter is secure when you run it- clamp it in a vise if possible.

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'83 300D, 126K miles.