91 larson 4.3 wiring issues

[thegoat86]

Traded for a Larson boat, now I have found some issues with the wiring. I cant get the boat to shut off. I choke it out through carb to kill. Tested the ign switch, shuts off continuity fine, but I have a back feed when running. Feel it is wiring where the motor was replaced. I have a few other wires curiously not hooked up as well. Plus the fuel pump is wired to the coil +. I read it should run through the oil pressure switch?? I tried Iboats manuals but cant find the appropriate diagram for the 4.3 vortec. soooo any help would be greatly appreciated. thanks

 

[alldodge]

Traded for a Larson boat, now I have found some issues with the wiring. I cant get the boat to shut off. I choke it out through carb to kill. Tested the ign switch, shuts off continuity fine, but I have a back feed when running. Feel it is wiring where the motor was replaced. I have a few other wires curiously not hooked up as well. Plus the fuel pump is wired to the coil +. I read it should run through the oil pressure switch?? I tried Iboats manuals but cant find the appropriate diagram for the 4.3 vortec. soooo any help would be greatly appreciated. thanks

:welcome: to iboats

http://www.boatfix.com/merc/Servmanl/13/13E4R2.PDF

Could use an engine serial number, can you provide it?

 

[thegoat86]

Awesome. But the schematic you linked is for the 3.0 motors. The pic on your reply is what I need. But I cant see the wire colors. Cant blow it up either without distorting the pic. I will look for the motor number

 

[thegoat86]

engine serial is 0D510496. I just checked the alternator wiring. The sense and ignition wires were backwards. I fixed and still no change. Starts great, runs fine, but will not shut down with the key. I checked voltage after I shut off the key and I have 15 volts at the purple ignition wire in the dash. That is def. a back feed. I traced the wiring, and based on what I can see, there are no shorts. The starter solenoid wire is not shorted, the relay is straight. I am missing something. And yes, I did disconnect the wires from the ignition switch again and double checked for continuity. Switch seems fine. Even when I take the purple wire off the switch the motor still runs.

 

[alldodge]

Awesome. But the schematic you linked is for the 3.0 motors. The pic on your reply is what I need. But I cant see the wire colors. Cant blow it up either without distorting the pic. I will look for the motor number

Wiring colors for 4, 6 or 8 cylinder engines are all the same. Here is another
http://www.boatfix.com/merc/Techbk/96/96HGD4.PDF

 

[Bt Doctur]

dis-connect all the wires from the alt and retest

 

[Bt Doctur]

 

[thegoat86]

My motor has an electric fuel pump. and I assume an aftermarket four barrel carb? It is four barrel for sure just don't know if it came with my motor.

Just disconnected the ign and sense wires from the alternator. The motor now shuts down with the key.:yield: What now? I will recheck all of my wiring again. I already swapped the sense and ign wires to the right spots...;... According to delco's alternator wiring diagram. Purple wire goes to black wire which is the ign+, red goes to the red wire which is the sense wire from the relay.

 

[thegoat86]

I do not see the oil pressure cutoff switch............

 

[thegoat86]

scratching my head. wondering how the alternator comes into play. And how disconnecting the wiring causes the problem to go away. And when I reconnect, the motor will not shut off. just continues to backfeed.

 

[Bt Doctur]

the alt is either wired backwards or it has a bad diode in it allowing it to backfeed the ign system
look down by the oil filter , see if there is a sender and a pressure switch "T" `d together
Ooops, my link is for standard fuel pump, not electric, same color code in alldodge`s #2 post

 

[thegoat86]

Sooooo.... It was the alternator. Bad diode. I am going to a one wire unit. Getting the other repaired so I can use it as a spare. Weirdest thing I have ever run into. I am looking for the oil pressure switch for the fuel pump. Not seeing one. Where would it be located? side?

 

[achris]

Port side of the engine, down under the exhaust manifold.

 

[Bt Doctur]