Mercruiser Ignition Interrupt

[Mach 1 Spitfire]

Hello boaters,
Does anyone know how the ignition interrupt works in the Mercruiser system? How does it instantly kill the ignition for a moment and have it still work when fully in gear?? My switch works good, I checked the continuity and it is good. It just looks like that when the switch contacts when going in drive, that the ignition would stay shorted out. My switch stays connected. I thought it would interrupt for just a moment then reconnect the circuit. Any ideas, or just a simple explanation of how it works as the cable moves would be great in comparison to the poor information found in the SELCO manual.

Thanks
Doug

 

[WizeOne]

Re: Mercruiser Ignition Interrupt

Hello boaters,
Does anyone know how the ignition interrupt works in the Mercruiser system? How does it instantly kill the ignition for a moment and have it still work when fully in gear?? My switch works good, I checked the continuity and it is good. It just looks like that when the switch contacts when going in drive, that the ignition would stay shorted out. My switch stays connected. I thought it would interrupt for just a moment then reconnect the circuit. Any ideas, or just a simple explanation of how it works as the cable moves would be great in comparison to the poor information found in the SELCO manual.

Thanks
Doug

T'would help if you posted exactly what you are working with. All interupt systems are apparently not created equal.

Also a very good idea not to publically post your email addy. In fact, it may not be allowed here.

 

[Don S]

Re: Mercruiser Ignition Interrupt

Head up to the ADULTS ONLY sticky at the top of the forum, then clidk on item #4 How the shift interrupt system works.

 

[Mach 1 Spitfire]

Re: Mercruiser Ignition Interrupt

Don,
Found it
Doug

 

[Don S]

Re: Mercruiser Ignition Interrupt

Well, did you understand it?

 

[Haut Medoc]

Re: Mercruiser Ignition Interrupt

Sounds like you have a bad lower shift cable, lubricating the pivot points on the linkage is never a bad idea either.....

 

[Mach 1 Spitfire]

Re: Mercruiser Ignition Interrupt

Don,
Well, found a new one on e-bay for $90, got lucky.
I have this problem fixed but am still not sure how the ignition interrupt works. I read the sticky but it really did not tell about how it actually cut the ignition out when connected to the white with green tracer wire on the distributor. I only know that the switch is either on or off. When the roller is in the v notch it shows no continuity, but when its on the cam (high point), it shows continuity. I would think the ignition would short out and stay grounded out. The shift cable works smooth.
Thanks for any professional advice.
Doug

 

[Don S]

Re: Mercruiser Ignition Interrupt

When the roller of the shift interrupt switch is in off position as shown in this picture, The switch is open (No continuity)

When it's on the high spots and closed, (Has Continuity) that is when the ignition is grounded and if held in that position, the engine will die.

When you try to shift back to neutral, the resistance causes the shift interrupt switch to activate. When it does, the engine tries to die (But, only for a split second) and pressure is released from the shift dogs, and it comes out of gear and the spring wires on the Y bracket, push it back to the open position again, as shown in the picture.
Just takes a split secon.
With a bad cable, it doesn't return to the position shown.

 

[Bondo]

Re: Mercruiser Ignition Interrupt

Ayuh,...

This is a repost of the answer I gave you in your Other Thread about this Same Issue....

When the roller is in the v notch it shows no continuity, but when its on the cam (high point), it shows continuity. I would think the ignition would short out and stay grounded out. The shift cable works smooth.

Ayuh,...

Only when shifting Out of gear,...
Only when the boat is In the water,....
The switch should kick off,+ reset in an Instant....

If there's motion of the switch with the boat on the trialer, or the switch Doesn't reset Instantly,....
The cable is dragging,+ needs replacement...

 

[Mach 1 Spitfire]

Re: Mercruiser Ignition Interrupt

Don and Bond-o,
Well that is a fast acting part. I will look at its action when I have someone shift it for me. I think I will see the action and then figure it how it moves, just kind of hard to imagine. Right now I am painting the transome, gimbal and bellhousing, got it all apart and what a job. Putting in a new cable, bellows and trim switches etc. Do you know of any other technical manuals out there other that CLYMER & SELOC?
Thanks for all the info and help
Doug

 

[Mach 1 Spitfire]

Re: Mercruiser Ignition Interrupt

Bond-O,
When I get it all back together, can I manually shift the unit sitting in the shop to see it move? (without it running) So why does the boat have to be in the water like I have noticed you saying? Also, why does the water affect the movement of the cam and switch as opposed to on the trailer?? Is there a manual that lays all this out?
Thanks
Doug

 

[Don S]

Re: Mercruiser Ignition Interrupt

There are links to manual in the Adults Only sticky at the top of the forum, did you look at the info I mentioned earlier in this thread???
The manuals will NOT give you detailed information of how it works, only how to adjust and repair the parts.
Yes, you can go back and move the parts when the engine is running to see how it works. If you push the switch the engine will die if you hold it long enough. But you won't hurt anything.

 

[Bondo]

Re: Mercruiser Ignition Interrupt

So why does the boat have to be in the water like I have noticed you saying? Also, why does the water affect the movement of the cam and switch as opposed to on the trailer??

Ayuh,...

It Only works when coming Out of gear,...
And,..
It's the resistence of the Water, aka. the Load against the Prop that causes it to Work...

No Load, No motion of the switch...

 

[Fishermark]

Re: Mercruiser Ignition Interrupt

As mentioned above, the load or pressure from the water keeps the clutch from easilty disengaging. the engine has to "stumble" to release the pressure. On land there is no pressure on the clutch and it will come out of gear easily.

I believe Don S or someone posted a video clip that shows a cutaway - I don't remember if this is it or not... it is a Cobra, but it is the same principle:
http://www.youtube.com/watch?v=vuAcrDFvApA

 

[Mach 1 Spitfire]

Re: Mercruiser Ignition Interrupt

Professional boaters,
Great info and, thanks for your being patient with me on these restoration questions. It has has been a large learning experience for me. A little different than working on the old '57 Chevy. I have another question on the ignition that I will post on another thread.
Doug