79 Mercruiser no start (120)

I'll try to make a long story short.
Get to fishing spot, turn motor off, drop anchors. Decide I want to reposition. Turn key and nothing, no click or nothing. Notice gauges work, fish finder direct wired to battery works. Didn't have test light in tool box, so I unhook fishfinder positive from battery and touch to pos at starter, have power. Touch to "in" side of slave solenoid, have power. Turn ignition on and touch other side of solenoid nothing. So I make a jumper cable, jump across the solenoid turn key and it starts. So we shut it down, finish fishing, then jump the solenoid to start it and head home.
Jump forward to today. With a new solenoid in hand, I install it and again, no start... take apart cc and check power at ignition. Have a blown 30amp to ignition so I replace it, the wire, and the whole ignition switch. Still no start. Start thinking it's the neutral start safety switch. So, I jump the solenoid, start the boat, then depress the neutral start safety switch and the boat dies. So I guess the switch is working.
So I am stuck, can't get the dang boat to start.....
I do have the manual and it points out the following
- Control lever not in neutral position....It is
- Battery charge low, damaged wire, loose connection...battery charge is fine, can't find any loose or damaged wires
- Curcuit breaker tripped....nope.
- Ignition Switch.....replaced.
- Faulty neutral safety switch..I believe my test above rules this out.
- Starter solenoid....but if I jump the slave solenoid and it starts..........
- Slave solenoid....replaced.
- Starter motor....but it works when I jump the slave solenoid...
Any help would be greatly appreciated.
I do have a fancy powered test meter, but I haven't read the 1 inch thick manual yet. Been relying on a test light.

Re: 79 Mercruiser no start (120)

Neutral safety is in the control box, shift interlock is mounted on the motor.

Re: 79 Mercruiser no start (120)

Bt Doctur said:

Neutral safety is in the control box, shift interlock is mounted on the motor.

Click to expand...

Could you explain a little more?
I guess when I thought I was messing with the neutral safety switch, I was actually messing with the shift cutout switch.

thanks.

Re: 79 Mercruiser no start (120)

I tried moving the shifter up and down in neutral while turning the ignition and got nothing. So I decided to check the 30 amp fuse I had replaced and it was blown again. Put in a new one, check power at ingnition switch and it was good, turned key to start and fuse blew again. So it looks like I have a short. Any pointer on where and how to start?

Thanks

Re: 79 Mercruiser no start (120)

This might help isolate it, pull the main harness plug at the engine, replace fuse and test ign and start position.Fuse blows, trouble is in the dash area, fuse dosent blow, trouble is in the engine area
http://www.boatfix.com/merc/Techbk/96/96HGD4.PDF

Re: 79 Mercruiser no start (120)

Bt Doctur said:

This might help isolate it, pull the main harness plug at the engine, replace fuse and test ign and start position.Fuse blows, trouble is in the dash area, fuse dosent blow, trouble is in the engine area
http://www.boatfix.com/merc/Techbk/96/96HGD4.PDF

Click to expand...

Thanks a lot for giving me a place to start!!

Re: 79 Mercruiser no start (120)

Bt Doctur said:

This might help isolate it, pull the main harness plug at the engine, replace fuse and test ign and start position.Fuse blows, trouble is in the dash area, fuse dosent blow, trouble is in the engine area
http://www.boatfix.com/merc/Techbk/96/96HGD4.PDF

Click to expand...

Does that have the 120 in it?

Re: 79 Mercruiser no start (120)

May have to substitute a bit for the points but for the most part there the same as the 3.0. Dash wiring is pretty standard.You need to isolate it first and then we can offer suggestions.

Re: 79 Mercruiser no start (120)

Bt Doctur said:

This might help isolate it, pull the main harness plug at the engine, replace fuse and test ign and start position.Fuse blows, trouble is in the dash area, fuse dosent blow, trouble is in the engine area
http://www.boatfix.com/merc/Techbk/96/96HGD4.PDF

Click to expand...

When I pull the main harness plug I have no power at the console. The power seems to run from back to front, then back to the motor. Any other suggestions?

Re: 79 Mercruiser no start (120)

Ok, I had to hook the main harness back up to get power to the console. Here is what I know now. I have power to the ignition switch when the key is in off position. I have power to the ignition switch when the key is turned to accessory, I have power to the ignition switch when the key is turned to on. Once I turn the key to start, it blows the fuse.
Amy more ideas of where to look?

Re: 79 Mercruiser no start (120)

Update,
I decided to isolate at the ignition switch. First I unhooked the "Ignition" side, put in a good fuse, turned to start and blew fuse. Unhook "Batt" at ignition switch, put in new fuse, and turned to start, fuse did not blow, so I figured it was that wire. This wire is the one going to the neutral safety switch. I followed it and realize some one had purposely crossed the wire going to the neutral safety switch and the one coming out. Once I seperated these two wires, I could turn the switch to start and the fuse would not blow, but the boat would still not turn over.
When I turn to start I have power going to the neutral safety switch, and power come from it. When I put it in gear and try to start I have no power from the neutral safety switch. So it seems to work.
I went back to the engine, I have power to the hot side of the starter and slave solenoid, but when the key is turned to start, I have no power on the "out" side of the slave solenoid. Shouldn't I have power from there back to the starter when the switch is turned?
I really need some help guys.

Thanks

Re: 79 Mercruiser no start (120)

New update,
I went back to deal with the slave solenoid. I pull the manual for the 120 and decided to try to test the old solenoid that I had removed. I followed the instructions and it seemed to test fine. This led me to believe it was never the solenoid. Originally when I ?jumped? the solenoid to start the boat, I jumped from the 12 volt from batt terminal to the 12 volts to starter terminal. I decide to try one more time, this time jumping from the 12 volt from batt terminal to the ?From key switch (12 volt in start position)? terminal and the starter kicked over. Still not sure what to do I walked to the console, turned the key and the damn thing started!! Turned it off and restarted two more times. Now, I?m glad it starts, but how in the hell did I fix it? I?d hate to be on the lake just to have it happen again.
So, any ideas now?

Re: 79 Mercruiser no start (120)

my first thought was maybe you got the wrong solenoid. Many look the same but have different configurations. Next thought was did you have it wired correctly as you stated someone had jumped the safety switch which was causing your fuse to blow. Could it be by following the manual you now have it wired correctly and it should work fine from now on?...

Re: 79 Mercruiser no start (120)

Well I didn't change how the solenoid was wired. It would not turn over, I jump the solenoid once, try to start and it started. It starts everytime now. I'm at a loss. I'm afraid some thing is loose and once I hit the water it'll go out on me again...

Re: 79 Mercruiser no start (120)

It's an older boat. Wiring does corrode. Maybe a wiggle test through out the harness? I know, needle in a haystack. Sometimes that's the case. Start with the weakst links. Battery cables in good shape and clean at both ends? Starter connections clean/shiny and tight. Cannon plug clean and tight? How about the safety kill switch wiring is now proper clean and tight? (soldered and not twisted by finger and wrapped with elec tape). Electrical can be frustrating....good luck..be patient.