electrical issues i need some help

[allious]

i have a 1998 mercruiser 7.4l engine. the boat had some water get to the wires behind the dash. it would crank sometimes but not very often. the wires were corroded badly. anyway yesterday, i did away with the 2 electrical plug harnesses that were damaged and cut out some of the badly corroded wires. i thought that would solve the problem. but it hasn't totally fixed it. it now constantly has electricity flowing to the switch and coming out of the switch to the yellow/red wire but even though the switch comes "on" and is getting electricity to the yellow/red wire the starter will not turn over now. also the tilt trim is now not working after working earlier. my question is where does the yellow/red wire go to to cause the starter to turn over and engage? does it go to the ecm or the starter or where?

 

[ken_23434]

Re: electrical issues i need some help

Here is a picture that was titled "Typical Starting System".

 

[ken_23434]

Re: electrical issues i need some help

Here is the description of current flow according to the Mercruiser Service manual

• Battery to the solenoid switch (on starter) (RED battery cable)
• Solenoid switch to circuit breaker (RED)
• Circuit breaker to wire junction (RED-PUR)
• Wire junction to wiring harness lug (RED-PUR) terminal 6
• Wiring harness plug to 20 amp fuse (RED-PUR)
• 20 amp fuse to ignition switch terminal I (RED-PUR). At this point ignition switch is turned to START.
• Ignition switch terminal I to terminal C
• Ignition switch terminal C to neutral start switch (YEL-RED). NEUTRAL START SWITCH MUST BE AT NEUTRAL POSITION.
• Neutral Start switch to wiring harness plug terminal 7 (YEL-RED)
• Wiring harness plug to starter solenoid (small terminal) (YEL-RED). Also ensure thatblack (small terminal) wire is grounded
• Starter solenoid is now "closed" completing circuit between large terminal (RED-PUR) and other large terminal (YEL-RED), causing starter motor to crank

 

[ken_23434]

Re: electrical issues i need some help

You can download the official Mercruiser Service manuals at the --Adults Only -- sticky at the top of the forum. The service manual will have the wiring diagrams and troubleshooting guidance.

That's where all my "knowledge" comes from.

 

[allious]

Re: electrical issues i need some help

ken where is the 20 amp fuse located? is it in engine bay or in fuse panel up front?

 

[ken_23434]

Re: electrical issues i need some help

I would look for it in the **** pit area. In that drawing, it shows it as an inline fuse. But, all that really depends on how they did it when they built your boat. That image I posted and the list of tracing the power were taken from one of the Mercruiser service manuals.

If you have corrosion on any of the connections or any of them are loose, that can cause a large resistance and effecitively "drop" the voltage at that point. If you have the 12 volts at the ignition switch, I would next check the wire downstream of the neutral safety switch in the throttle. That switch is a safety item to make sure the engine is not in gear when starting the boat. Either that, or put your volt meter on the starter solenoid to see if the 12 volt signal is getting to it.