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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10601
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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1993 Four Winns with 5.0L OMC cobra engine, ignition/staring

Customer Question

1993 Four Winns with 5.0L OMC cobra engine, ignition/staring issue.
I just bought this from a family member. The key started the engine the first 3 times then would not work. Tee key switch was replaced just before we bought the boat. If I turn the key to "ON" and pull the cover off the engine and short the starter terminals with a screw driver, the engine starts instantly and runs very smooth. (3 hours cruise without issues)
I did pull the start switch and look at the terminals and plan to replace then eyelets and put electrolytic grease on them but wanted to ask you for any additional advice before I go an hour to where the bout is in its slip.
Also, I put a meter on the switch and see where on side does make contact when I turn the key to ON, but did not see any transition with any combinations on the terminals when i turned the key to START. It could have been the way I was holding the meter probes while trying to turn the key.
Any ideas?
Submitted: 3 months ago.
Category: Boat
Expert:  Tan replied 3 months ago.

Hello. My name is Tan.

There are some circuit breakers on the engine have you checked the circuit breakers. These are the large red buttons. Push real hard to reset if tripped.

Customer: replied 3 months ago.
Hi, Tan-
YES. I have push the breakers and they do not seem to have been tripped. There is no change after I push the red rest buttons.
Expert:  Tan replied 3 months ago.

Good morning Ed. Do you have a volt meter to do some voltage tests? We need to test for voltage at the red wire at the key switch, then at the yellow/red on key switch with key in crank position? Do you have voltage at both on neither?

Customer: replied 3 months ago.
Tan,YES, I have a good Fluke meter that will be with me on the boat this afternoon. The wires on the key switch have been replaced and there is no longer a red wire but I can trace it back to the distribution panel.NOTE: The key switch DOES work to control the radio, lights, etc. The only issue is the start function. My plan for today includes changing the tarnished wire lugs on the wires attached to the key switch.Ed
Customer: replied 3 months ago.
HOW to preform a test similar to a hot wire jump start? I can email you some jpg's later if it would help.
Expert:  Tan replied 3 months ago.

Ok long as we have voltage at the key switch and the switch is new then we need to test for voltage on the slave solenoid yellow/red wire key in crank position.

I will be here all day so just post back when you the test done.

If you have no voltage on the yellow/red then you have a bad neutral safety switch. If you have voltage there test for voltage on the large yellow/red and the red large terminals on the slave solenoid. Do you have voltage?

Post back with findings.

Customer: replied 3 months ago.
OK will do. OAO.
Expert:  Tan replied 3 months ago.


Customer: replied 3 months ago.
Red wire found. With key in ON position:
From red to yellow/red-stripe 12 vdc. When key turned to momentary start position voltage drops to 0 (zero) vdc.
FromYellow-red-stripe to orange 12 vdc. When key turned to momentray start position , the voltage dtops to 0(zero) vdc.
Cleaned and greased all contacts.
Result- no change, key still does not cause engine to start.
Expert:  Tan replied 3 months ago.

Hello Ed. We need to go to the circuit breakers and test the voltage on both terminals when key is in the crank position. We have voltage loss due to a bad connection, bad breaker or bad wire.

Do this tes with you ground test lead on good engine ground and the battery negative terminal. We need to eliminate a possible bad ground issue.

Customer: replied 3 months ago.
Ok. Will do this tomorrow. Thank you.
Expert:  Tan replied 3 months ago.

Ok Ed I will be available.

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