3.0ltr Engine starts but dies when key in run position. Also no power to instruments

[Hoosmatroos]

Hello all,

I'm currently at a boat with a Mercruiser 3.0 s/n: 0B917460

The boat was sitting for two years after proper maintenance. But, when we hit the key the motor starts and run oke for the time that you held the key. If you let the key switch back to the run position the motor dies. There is also no power to the instruments. So it starts but won't run with the key in the on position.

I don't have a manual at hand but hope you can tell me where to look.

Thanks

 

[Bt Doctur]

look under the dash for a fuse in the purple wire at the key switch. with the key "on" there must be 12v at the coil +

 

[Fun Times]

Sounds like the key switch is defective internally. Try Jumping the wires behind the switch to see if it will run. Red wire to Purple for ignition. Then touch Red to Yellow till engine is started/running.

0B917460 looks to be a 1988 Mercruiser 3.0L [ALPHA] W/ PS
http://www.crowleymarine.com/mercury-outboard/963.cfm?mdl=3GZ1YX&q=0B917460

 

[thumpar]

Is this a points engine or digital?

 

[bruceb58]

Check your man overboard switch.

 

[Hoosmatroos]

Is this a points engine or digital?

This is a points engine.

Thnx so far. I'll check the suggested items and let you know.

 

[thumpar]

This is a points engine.

Thnx so far. I'll check the suggested items and let you know.

Check to make sure you have 7-9 volts at the coil with the key on (not start, just run).

 

[bruceb58]

If he doesn't getting power to his instruments, he won't be getting power to the coil.

Also, he could have either 12V at the coil or 7-9V(depends on the points open or closed) once he figures out the issue.

 

[stonyloam]

You are not getting 12v from the ignition switch to the instruments or coil resistance wire. Start by checking for voltage at the purple wire on the back of the ignition switch, with the switch on.

 

[nola mike]

^^^^^What he said.
With key in start, you get voltage to the coil through your slave solenoid, so it starts. When you let go, you depend on the wire back from the ignition to power the coil.

 

[fishrdan]

Check the (50 amp?) breaker on the engine and 90 amp fuse on the starter.

 

[bruceb58]

Check the (50 amp?) breaker on the engine and 90 amp fuse on the starter.

That is true as well. Could check the voltage at the input of the ignition switch first and if it is isn't there, go and check those items.

 

[Hoosmatroos]

I'll go back to the boat in one hour to help the guy with his problem. I've checked the diagrams and it shouldn't been hard to find out what is wrong. Let you know.

 

[Barnacle_Bill]

First thing I'd check is the ballast resistor

 

[bruceb58]

First thing I'd check is the ballast resistor

That would not explain no power to instruments. It's way up stream from the ballast resistor.

 

[Hoosmatroos]

O.K. guys, after unscrewing the dash it scarred the sh!t out of me. What a mess!! You know the term spaghetti wiring?

Armed with my multimeter I followed the lead from the key switch. 12V present. That was easy because the switch worked to start the engine. In run position also 12V at the other end but not on the coil. Followed the lead that changed color 2 times (from red to black to brown!!) in the spaghetti to the MOB switch. 12V present. But not on the other side! Removed the plug and pushed the switch manually and yes, connection. Asked the guy to push the switch and then also voltage on the coil. Simple as it can be, MOB switch faulty.

Thanks for the help!