Engine shifts into gear, hard to shift out of gear

[Limited-Time]

Re: Engine shifts into gear, hard to shift out of gear

In the diagram Don posted the purple wire feeds the dist the required voltage through the Shift Cutout Switch (SCS). The SCS id normally closed. When the SCS activates it breaks the supply voltage causing the engine to "stumble" allowing the dog clutches to disengage. There is no tie to ground.

 

[81 Checkmate]

Re: Engine shifts into gear, hard to shift out of gear

No do not put a larger amp fuse. Something is causing the fuse to blow. Most of the time when fuses blow it is a grounding issue. I would wait for Don to chime in and see what he says.

Looks to me it still is an wireing issue. Not to knock down the EST system, is that i just didnt like the set up.

Thats why i went with the Mallory unit when my Thunderbolt system went out. It was almost the same as my stock set up except for the control module is in the Dist. Plus it has an external coil.

I am sure Don will get you straightend out.

 

[greg82255]

Re: Engine shifts into gear, hard to shift out of gear

I thought I read somewhere that the ignition gets grounded and that's why the motor stalls - that's the only reason I said that. I guess I misread whatever article/thread I got it from. I thought I had it setup exactly as the second diagram shows. Here is exactly what I did:

I took a purple wire, as suggested, and connected one end to the purple wire from the wiring harness (same wire that goes to the coil). Then I connected the other end of this purple wire to a black wire coming from the interrupt switch. Then I took the single black wire coming from the distributor and connected it to the grey wire coming from the interrupt switch. One end of the switch went to the distributor, and the other went to the purple wire (power). Now when I press the switch, the fuse blows and the engine dies. Did I hook it up incorrectly?

I should also point out that there was a green/white wire that used to be connected to the thunderbolt distributor that is no longer connected to anything. There was also a black wire previously connected to the grey wire coming from the interrupt switch (described above) that is also no longer connected to anything. I temporarily covered the ends of those wires with electrical tape in order to test the new setup .

 

[Don S]

Re: Engine shifts into gear, hard to shift out of gear

I took a purple wire, as suggested, and connected one end to the purple wire from the wiring harness (same wire that goes to the coil). Then I connected the other end of this purple wire to a black wire coming from the interrupt switch. Then I took the single black wire coming from the distributor and connected it to the grey wire coming from the interrupt switch. One end of the switch went to the distributor, and the other went to the purple wire (power). Now when I press the switch, the fuse blows and the engine dies. Did I hook it up incorrectly?

Yes, you hooked it up right. The problem is, one little minor detail.. Just seems insignificant really, but the cause of the blown fuse.
So, here is your electrical quiz of day. What causes a short. Answer: power to ground.
You had an electrical system as in my first picture in reply #15, you then hooked it up as in the second picture, right. Hooking the wires to the terminal block, just like shown in the second picture, right? If so, .......... you have a Dead short. WHY ????

 

[greg82255]

Re: Engine shifts into gear, hard to shift out of gear

I did connect them at the terminal block.. I thought about that immediately after my last post. You are saying that is causing the problem? I'll hook them up outside of the terminal block. I assume the terminal block is grounded, which is the cause of my problem... Am I right?

 

[Don S]

Re: Engine shifts into gear, hard to shift out of gear

You're right.

 

[greg82255]

Re: Engine shifts into gear, hard to shift out of gear

Alright, I'll fix the problem tomorrow and report back. Thanks Don for all your help.

 

[greg82255]

Re: Engine shifts into gear, hard to shift out of gear

Now I remember where I read that the ignition is grounded when the switch is activated. From the Adults Only section on the shift interrupter:

"When this Y plate moves and activates the shift interrupt switch, the ignition coil is grounded and the engine starts to die due to lack of spark, and pressure on the shift dog is released."

I assume there must be a difference between grounding the ignition coil and grounding the ignition?

 

[greg82255]

Re: Engine shifts into gear, hard to shift out of gear

Went out to the boat today, disconnected the wires from the terminal block. Problem solved. Shift interrupt works, easy to shift in and out of gear, no more blown fuses. Thanks Don for all your help.

 

[Don S]

Re: Engine shifts into gear, hard to shift out of gear

I knew that would cure your problem.

Now I remember where I read that the ignition is grounded when the switch is activated. From the Adults Only section on the shift interrupter:

"When this Y plate moves and activates the shift interrupt switch, the ignition coil is grounded and the engine starts to die due to lack of spark, and pressure on the shift dog is released."

I assume there must be a difference between grounding the ignition coil and grounding the ignition?

There is the problem, that is true in most all Mercruisers, including yours, right up to the point that you replaced the OEM system with something that Mercruiser never used on a V8.
On every carbed Mercruiser V8 engine since Merc started, the ignition was grounded. The only engine using the EST was the 3.0L engine, and it had seperate instructions.
When you want to change an ignition system, other things have to change to make it work.
With the EST, grounding doesn't work, even if you want it to.