Ayuh,..... That is Not original,.....
Boat throttles really don't need any spring, at all,.....
The throttle cable should, when adjusted correctly, put a slight tension on the linkage to hold it tight against the idle adjustment screw,.....
It shouldn't need a return to idle spring,.... 'n...
Ayuh,...... The key switch should have a B (battery) terminal, red wire, 12v, all the time,.....
A S (start) terminal, yellow/ red wire, 12v only in the start position,....
A I (ignition) terminal, purple wire, 12v in the run position,.....
The Start circuit yellow/ red wire feeds the slave...
Ayuh,..... Welcome Aboard,..... Switch yer meter to dc voltage,.....
Ignition power goes from the key switch to the wire at the choke, to the coil,.....
When starting, ignition power is also supplied by the outside tiny terminal of the starter's solenoid,....
All that appears right...
Ayuh,.... Sounds more like an ole AQ Volvo,....
Step back, 'n take some more pictures of the drive, 'n motor,.....
Got some serial / model numbers,..??..??
Ayuh,..... Sell the OMC stuff, 'n buy yerself a complete running Merc or Volvo in a rotten hull, then swap the entire driveline, pulleys to prop, into yer hull,.....
The only thing that OMC has in common with either a Merc or Volvo is the motor's Long Block,......
Ayuh,.... Welcome Aboard,.... The problem yer gonna have is tryin' to marry up the outlets to that stringer drive outlets,.....
Volvo had 280 drives,.... OMC used Stringer drives,..... Not the same,....
Ayuh,..... Backtrack to the tank,...... Is the anti-siphon valve at the outlet clear,..??
Is the dip tube to the bottom of the tank clear,..??
Prefill the fuel filter abit, as the fuel pumps gas, better than air,.....