Mercruiser 4.3 LX not firing

[Eddiez0803]

I've got a Mercruiser 4.3 LX in a 1989 Baja but can't get it to fire. Replaced the engine and it worked great. Then I rebuilt the outdrive and it's not working. It turns and turns, but nothing. I did the coil test and replaced the module inside the new distributor. Could it be the ignition amplifier (triangular part that says Thunderbolt IV and v6-14)? Is there a way to bypass this just to get it to fire to determine if that's the part?

 

[alldodge]

Did you happen to trip the kill switch?
Check for 12V on the + side of the coil

 

[Rick Stephens]

Shift interrupt?

 

[Eddiez0803]

Did you happen to trip the kill switch?
Check for 12V on the + side of the coil

No kill switch besides the key... I guess maybe the ignition switch itself could be faulty?

 

[Eddiez0803]

Shift interrupt?

What's that? Ha

 

[alldodge]

Need a voltmeter and see if there is 12V on the coil with key ON

If you have an Alpha outdrive, then the interrupter is on the shift plate

 

[Eddiez0803]

Shift interrupt?

 

[Rick Stephens]

HOW TO: How the Shift Interrupt system works

Usually in the spring and summer we get a lot of posts regarding the shift system for the MC-1 (falsely referred to as Pre-alpha drives) to the Alpha 1 drives. There are a lot of wrong ideas on how and why the system works and why it's there to begin with. Maybe this will help explain how it...

forums.iboats.com

 

[Eddiez0803]

Need a voltmeter and see if there is 12V on the coil with key ON

If you have an Alpha outdrive, then the interrupter is on the shift plate

Yea it's an Alpha 1. The interrupter is on the drive shifter (forward/reverse right?) but since the starter turns, id assume that isn't messed up, right? When I'm in forward gear, it won't spin the starter - in neutral it will. Could the part in the photo attached here be causing the issue? Maybe it's bad?

 

[alldodge]

Yea it's an Alpha 1. The interrupter is on the drive shifter (forward/reverse right?) but since the starter turns, id assume that isn't messed up, right? When I'm in forward gear, it won't spin the starter - in neutral it will.

Did you read the link Rick left in post 8?

Could the part in the photo attached here be causing the issue? Maybe it's bad?

Yes, but so could every other part in the ignition system. If you test then it can be narrowed down, otherwise buying and throwing parts at the problem may fix it, but may also add more problems

 

[Eric 3.7LX Alpha 1]

Your here on a forum because you want to fix it yourself rather than send it in to a shop. Your going to have to invest in some tools to troubleshoot the problem. You need a way to test voltage. A 12-volt test light will do it, but I prefer a digital multi meter. You can check more with the meter, things like continuity, resistance, and amp draw, besides voltage.

You should also get a spark tester. They sell inline testers (like the Lisle #20610) and ones that can show if you have spark by touching any spark plug wire without disconnecting (like the Lisle #19380). I have and use both.

The shift interruptor does nothing to the starter circuit, it grounds the ignition and kills spark, same with the man overboard switch some boats have that you clip yourself to. The neutral safety switch in the shifter at the helm would break the starter circuit... as in, won't let you crank the engine over if the shifter isn't in neutral.

 

[Eric 3.7LX Alpha 1]

This is from the Mercruiser service manual #7 for your engine: