Re: ELEC. Starting sys. ?
Iwould think that most use a "slave" because of the thin wire used in boats.
without one you might melt the wiring harness.
this is not true, and it doesn't quite work that way.
so before everyone starts quoting boats use thin wiring...
there are different types of starters in regards to how it engages the pinion to the flywheel. The old direct drive style starters had the bendix drive, where as soon as you gave the starter power and it spun the pinion would shoot forward. In this case, the starter solenoid was just that, a high current switch. So all you need is the one solenoid (either mounted on the starter or remote mounted) and the wire from the starter switch went directly to it. This type of solenoid draws low current, so you can use 10-20 feet of 14-16 gauge wire from your ignition switch to it and have it work.
late model starters, the PMGR (permanent magnet gear reduction), do not use a bendix drive. instead, there's a fork that slides the pinion to engage/retract it and the fork is controlled by the solenoid on the starter. This solenoid is also an electromagnet. So when you give this solenoid power, it acts as a high current switch to power the starter at 50+ amps but it also consumes a good deal of power itself to move the plunger in it to engage the pinion. For this solenoid, you cannot just wire your starter switch to it with 14-16 gauge wire. There will be too large a voltage drop along it and you'll actually ruin the starter solenoid long before there's enough current to melt anything. For this type of solenoid you also need a slave solenoid, where the slave solenoid has the wire from the starter switch and it draws low current, and the high current side of it has 10-gauge wire coming from the battery going to the starter solenoid and the wire distance is short so the starter solenoid can get full voltage and current to operate properly.
Thanks