Motor Cranking in "On/Accessories" Position (Stern-drive Engine)

[Croskey2010]

Hey everyone,

This one is a bit of a doosie... I just recently bought a new Throttle Control box for a 1991 Mercruiser Stern-drive (350 Chevy 5.7L)

I have not changed any wiring at all and had no problems what so ever until the new control box was added last week.

The new box had one less wire for my trim controls (red, green, and blue are used and Purple was left out) Trim works greats and correctly.

Then I have the neutral safety lines coming out of the control box to the existing lines in my boat. I have gone through 8 different fuses trying to figure out what went wrong and even replaced the ignition thinking that it was the problem.

I have verified that I have continuity on my yellow/red wire to the control box and checked the continuity on the new ignition and it works correctly.

The problem is that when I turn the key to the on position (not start) the motor begins to crank... When shifted into gear the engine will not start. I haven't let the boat crank for more than about 1-2 seconds for fear that my starter will stay engaged. Or that the engine may not want to shut off.

I have three terminals on the back of the ignition
1. Battery - Red
2. Ignition - Yellow/red
3. Solenoid - Purple

Any help would be greatly appreciated. I will say that I have tried just about every combination under the sun thinking that the previous owner may have Jerry Rigged something incorrectly but everything seems to match the diagrams I am using.

 

[Chris1956]

Looks like you have the yellow/red and purple wires switched on the ign switch.

The ignition terminal on the ign switch runs accessories and is connected to purple wire.

The solenoid terminal on the ign switch should be connected with a separate wire to the neutral switch. The other side of the neutral switch should be connected to the yellow/red starter solenoid wire.

 

[Croskey2010]

We have tried that swap but when we do it blows the fuse and burnt up the battery wire on the ignition. For something with only three wires Im having an issue. I am wondering what would cause the the fuse to continue to blow in that position??

 

[kenny nunez]

You may have some of the wires pinched together in the control box. If everything worked before you changed it then that is where to look.
Why did you have to change the box?

 

[Nospark]

No spark 5.0 cobra

 

[Croskey2010]

You may have some of the wires pinched together in the control box. If everything worked before you changed it then that is where to look.
Why did you have to change the box?

So I found the short in my wiring... no idea how it happened. Somewhere from the wiring harness in the engine to the dash cluster my purple ignition wire and yellow/red solenoid wire are touching.

we tried to create the ignition circuit in the back of the boat in the engine bay and got the motor to crank but it wouldnt start. Not sure if we flooded it or its just being just stubborn.

Also I went ahead and bought a new ignition coil because why not... just one less thing to track down or do in the future.

 

[Croskey2010]

No spark 5.0 cobra

Check your ignition coil, or you can go to Harbor Freight and they have a distributor cap tester. if both of those are fine I would say to take a look at your sparkplug and make sure that their tolerances look right. If its not that then check your plug wires upgrading those can make a huge difference they could be worn out and old (also a cheap fix)

 

[kenny nunez]

Sometimes when the screws for the rub rail were drilled the bit penetrates the engine harness. Usually this shows up on a new boat but anything can happen over time.