[QUOTE=AllDodge;4762140]If you where jumping at the starter and not the slave relay, then the starter may be the issue
Did you jump from the starter post to the yellow/red wire on the inside of the starter?

I like that picture. lol. Wire from yellow/red to the big red wire. Sparks, jumper wire got hot. Starter did not kick in.
Fing starter is like $400+

I would recommend this starter, its PMGR so it lighter and easier to install. Do torque bolts to 50 ft lb and I would recommend new bolts

I have same one on my 509

Delco PMGR used on Mercruiser 500 Bulldog, 500EFI, 525EFI, 575SCI, 600SCI, 700 SCI & Scorpian 37 Eng | API Marine Inc

Edit: search for API 10105 and can find for less like on ebay

With the sparks flying this should also mean the slave relay is bad or fuse is blown. When you jumped the two points is the same thing that the relay does when the key is turned

I will try to swap the relays from SRTBD to port, easy to do, will see what happens. The slave relay is pretty cheap.

Jumping to start from the "Slave solenoid" got the starter to crank. Or least make a strong noise. I only did it for a second. OK. Next?/

Since jumping from the slave got the starter to crank over, then it should not be the starter. Probably means when jumping at the starter, the wire touched the ground instead of the solenoid excite connection. Turn key to ON and jump again to see if it will start. If it does then we know the starter is good.

Next need a voltmeter and see if you get 12V on the small yellow/red wire when key is turned to Start. If it does get 12V then the relay is bad or the ground wire on the other terminal of the relay is disconnected