1978 Mercruiser 120 won't run

[birchscott]

Hey folks. Just discovered this wonderful forum and now it is time for me to seek some advice (though please bare with me, as I'm a novice). Long story short I got this boat for free and everything is in good shape...minus the poor wooden seat frames. Anyways, I went to fire it up, fully expecting it not to start, and sure enough it didn't. Starter cranks, plugs spark, engine seems to fire, but only when the key is being turned. Letting go of the key kills the engine. Seems to be a fuel delivery problem, but other than that I have no idea. Are the fuel pumps on these engines electric or are they turned by the crank? Point me towards the appropriate direction and hopefully I can get this beast running. <br /><br />Thanks,<br />Scott Evangelist

 

[Bt Doctur]

Re: 1978 Mercruiser 120 won't run

pump should be mechanical,will run is start position, but not run position,might be a bad ballast resistor/wire .open ign.wire in harness.is there any voltage at the + side of the coil in "run"position?

 

[Bondo]

Re: 1978 Mercruiser 120 won't run

Welcome Aboard Scott,......<br /><br />We'll need to know What the Motor is,+ Who made the motor/ drive.........<br /><br />So Far,..... I Suspect a Wiring Issue.......

 

[birchscott]

Re: 1978 Mercruiser 120 won't run

Ahh yes...shoulda put that info in the body. Its a 1977-80 era Galaxy 18' with a 120 hp, 4 cyl I/O Mercruiser engine. <br /><br />Anyways, I did suspect the wiring. When I got the boat, every panel I could find was concealing countless numbers of black walnuts, a tasty treat for the local squirrels. Perhaps they played a role here... <br /><br />Bt Doctur I will check that tomorrow and get back to you.

 

[whywhyzed]

Re: 1978 Mercruiser 120 won't run

Resistor wire to the coil, or ignition keyswitch, or wiring anywhere in between.

 

[Don S]

Re: 1978 Mercruiser 120 won't run

To help in troubleshooting, what color and how many wires do you have going to the coils Positive terminal. They changed color coding in that time frame, sure would hate to have you looking for a color you don't have.<br /><br />One way to test to see if it will actually run is to put a jumper lead from the battery to the Positive terminal on the coil and start it up, if it does run, the problem is in the wiring. You will have to disconnect the jumper to shut it off.

 

[birchscott]

Re: 1978 Mercruiser 120 won't run

Turned out to be bad wiring at the ignition switch. Thanks a ton guys...you just made my month. I'll be sure to post some pics when I'm done refurbishing the boat. <br />Geeze, only a month til the 4th of July...I better get going on that.<br /><br />Thanks again,<br /><br />SRE

 

[boathog]

Re: 1978 Mercruiser 120 won't run

found the kill switch did ya!??