First time wiring engines ?'s

[legoman67]

Well, i am attempting to get my head around the wiring diagrams for our boat. The power is twin Merc 255MIE's Pre BIA code. Here is my questions:

1. Why does positive hook up to the negative and the positive terminals on the ammeter? can power pass through between the points?
2. where do the 2 wires in the diagram that are shown comming off the bottom of the alternator actually connect?
3. What do the B, A, C, and I stand for on the ignition switch? which one is what?
4. How do i tell which terminal is R and which is S on a non mercruiser starter?
5. How does the engine kill with these diagrams, it seems that the coil is hardwired to the battery and alternator, meaning it would be impossible to kill the engine?
6. What is the RESISTANCE CABLE? how is it different from a normal wire?

Thats all for now, any help would be appreciated

 

[tashasdaddy]

Re: First time wiring engines ?'s

you know Don S maybe able to help you. i/o forum.

 

[Silvertip]

Re: First time wiring engines ?'s

Ignition switch letters are as follows:

B = battery (+12 volts from the battery)
C = Choke (push key in to choke the engine -- generally outboards only)
A = Accessories (feeds the gauges -- +12 Volts with key ON-RUN position).
S = Starter (12Volts to the starter solenoid when key is turned to START)
m = mAGNETO - on outboard engines. Usually two of these terminals. They are shorted together with the key off. Kills and outboard mageto ignitiion.
I = Ignition. (Inboard/IO engines). Provides +12 volts to the ignition when the key is in the ON-RUN position.

Resistance wire is a piece of wire that has a specific amount of resistance rather being a straight piece of wire. It is fed to the coil to reduce voltage to the primary of the coil during RUN. The R terminal on the start solenoid bypasses this resistance wire during startup of the engine so the engine gets a full 12V for starting. Unless you are very fond of the ammeter, I suggest replacing it with a voltmeter so you don't need to use it and its heavy wiring. An ammeter reads total current passing through the system hence negative on one terminal, positive out the other. That gauge is in SERIES with the circuit. A voltmeter measures voltage ACROSS the circuit -- 12V to ground.